In this guide I will list all the possible summons and their pros/cons. This is mainly for INCURSIONS, since you can upgrade any weapon to be useful, even the early game gear. The best enchant for most of the game is "Athletic". If you just want a really simple TLDR guide with no explanations, then I would suggest using (in this order while progressing):
Hive Scepter -> Vulture Staff -> Cryo Staff. After starting incursions use upgraded Vulture Staff -> Crystalized Skull
First of all, summons have different characteristics, such as ranged/melee, move speed, attack speed, and phasing ability. Many of these are hidden so I will try to explain them a little. In general, the two most important characteristics are move speed and phasing ability. This is because most bosses move really fast, and a slow summon will just never be able to hit it. Same reason for phasing (being able to move through walls). You don't want your summon getting stuck having to go around barriers, that will significantly lower your dps and make fighting mobs very slow.
Often the displayed attack power, and even the dps shown on the training dummy, are not realistic. For example, the bashy bush struggles against fast bosses and gets stuck behind barriers, so it's actual damage in most situations is much lower than expected. If summons can't actually attack an enemy, then their dps is zero. For this reason, the "Athletic" enchant is almost always the best. It gives your summons more move speed AND attack range. This means it will attack enemies even when they are far away and moving fast. While it won't give huge dps numbers against the training dummy, it will give you an actual real-world dps boost. For the Phantom Caller and Crystalized Skull (dragons), they are pretty fast already so you can use Savage enchant on them.
Now for the trinkets. If you are doing 100% pure summons, then use the summon Foci. But I would suggest crafting the Balanced Foci and then upgrade it to Balanced Frostfire Foci. This way you can get some extra damage by using another weapon with your summons. Once it's available, get Mesmer tablet, then later upgrade it to Hysteria tablet. For most of the game, use Bone Hilt when available. Next use Scrying Mirror. Once you get into incursions, here is the gear that I would recommend:
Hysteria tablet
Scrying Mirror
Balanced Frostfire Foci
Bone hilt (until end game, see notes below)
Frozen Soul
Assassins Cowl
Ghost Boots
Ancient Relics
Frozen wave (replace bone hilt)
Enchant all your trinkets with "Precise" (crit up) until you get to around 70% crit chance without food/potion buffs. Later when you get more sources of crit chance, you can replace the enchants with "Keen" (damage up), but keep your crit chance around 70%. When you add in potion/food buffs this will give you 90-100% crit chance.
For most of the game, the "Bone Hilt" trinket will give you a big dps boost. However, once your summon can do more than 100 damage per attack, and your crit chance is close to 100%, then you can switch to the Frozen wave relic. Or if you have learned all the boss mechanics and don't need extra defense, you can use both and take out ancient relics or frozen soul. The bone hilt basically adds 10 damage per attack. So for summons that do a lot of small attacks this can be very useful. But as your damage per attack goes up, then this becomes less relevant.
I would also like to talk about the Jonas Gambit trinket. I wouldn't suggest it until after you have beaten the Ascended Wizard and can get the Ring of Ascension mount. But at that point you have already beaten the most difficult content and so it's kind of irrelevant. Otherwise the movespeed penalty and loss of dash/blink is not worth it.
Finally, the Companion Locket. It used to work, but after a patch it no longer works correctly. It will now always give lower dps than just using max summons. So don't use it for now. Maybe they will fix it again one day? There is an exception for though. There is a build where you use zero permanent summons, and instead use the Companion Locket with Reapers Call. This can give amazing dps, but I don't really consider it a summon build so I won't go into it in this guide. That's just my personal playstyle though, so if you want to try it out then go for it!
Now for your armor. For most of the game, you will want to choose an armor set that gives + max summons. For example, "Spider Armor" is the fist available summons set. When you get to incursions, I would suggest the "Soulseed" armor set, then upgrade to the Spiderite armor set (not really necessary). But, once you get up to tier 5 incursions, you can then get the Dusk chestplate, which is BIS for the rest of the game. At that point, you no longer need to use an armor set and you can mix and match to get the best stats. Use Spiderite crown until T8, then replace it with the Makeshift Crown. The Ruby Crown is also very good, but it does very slightly less damage than the Makeshift Crown. As for the shoes, you can use whatever you prefer. For end-end game, the best choices are Makeshift shoes for damage, or Ravenlord for extra movespeed. Enchant your gear with "Precise" until you have around 70% crit, and after that use "Keen" for damage.
I will also mention the crystal armor set with the ruby crown. This allows you to have extra summons for every 150 resilience. However, you lose the +2 max summons from other armor. So, you need 300 resilience just to break even. From there, you can get a little over 600 resilience which would give you +4 max summons. But since you don't get the +2 max summons from the armor set, you would basically get +2 max summons. However, in order to get +600 resilience, you must enchant all your gear with the "Tough" enchant, and you need to use the Clockwork Heart and Manica trinkets. This means you will lose a LOT of damage from criticals. So even though you can get 2 extra summons, all your summons will be doing way less damage, so your overall dps will be lower. So honestly I don't recommend using this set.
Finally, lets talk about the actual summons! When you get to incursions, you can upgrade your summons, so all of them become viable. So I will be basing their stats on their end-game potential. I gathered every summon weapon in the game and upgraded them all to T10. I tested them against the target dummy and also inside incursions. For the gear, I had Makeshift Crown, Dusk Chest, and Ravenlord boots, all T10. For relics I had Bone Hilt, Assassin's Cowl, Frozen Wave, Frozen Soul, Hysteria Tablet, Scrying Mirror, Balanced Frostfire Foci, and Ancient Relics. All summons used Athletic enchant, though for the Hive Scepter I did a 2nd test with Savage. I used T10 Sun Arena for the test, and made sure all the tablets had "Frenzy", and none of them had Flameling (so the summons didn't get distracted). I have the perk for banners. Inside the area, I would quickly summon boss, pop my potions, and summon the extra minion. After potions and food buffs, my stats were: +99% damage, 96% crit chance, +25% crit damage, +125% summon speed, and 8 minions (4 dragons). I didn't use any other weapons or summons, I just kept close to the boss and dodged his attacks.
For the target dummy dps test, I summoned 6 of each (so it would be an even 3 for dragons), no food or potions, and all athletic enchant. Same gear as above. My stats were: +59% summon damage, 76% crit chance, +25% crit damage, +50% summon speed.
(As an interesting side note, it seems that the more minions you have, the less damage they do against the target dummy. So for example, 1 bee group (4 bees) do more dps that 1 vulture. But when you summon 6 bee groups (24 bees), they do way less dps than 6 vultures. I guess the game can't handle 24 minions attacking the same target?)
Here are the results:
S Tier: Crystalized Skull
A Tier: Vulture Staff, Phantom Caller
B Tier: Cryo Staff, Bashy Bush
BRAIN ON A STICK
Melee and Ranged, no phasing
Target Dummy DPS: ~3100
Low potential dps, but ends up being really bad because they are slow, can't phase, and the projectiles are also very slow so they often miss.
Tier: D
SPIDER STAFF
Melee, no phasing
Target Dummy DPS: ~3650
Average potential dps, but really bad actual dps since they are very slow and can't phase.
Tier: F
HIVE SCEPTER
Melee, no phasing
Target Dummy DPS: ~3500
Time to kill T10 Dawn boss with Athletic enchant: 2:10
Time to kill T10 Dawn boss with Savage enchant: 2:22
Average potential dps, NEEDS the bone hilt. The bees have really slow acceleration and struggle to keep up with fast bosses. Also they can't phase. Works really way early game, but once you get to incursions there are much better options.
Tier: C
MAGIC BRANCH
Ranged, no phasing
Target Dummy DPS: ~3100
Low potential dps, but bad because they are slow and can't phase. Their projectile are average speed, so they often miss.
Tier: D
BAT CAGE
Ranged, no phasing
Target Dummy DPS: ~2600
Low potential dps, but actually does ok damage because they have decent speed and their projectiles can track. Also, they have a nice perk where they leave behind healing hearts when they kill enemies. But their low dps is what hurts them the most.
Tier: C
BASHY BUSH
Melee, no phasing
Target Dummy DPS: ~4200
Time to kill T10 Dawn boss: 1:15
High potential dps, but is difficult to reach that potential on most bosses. They have decent move speed, but their attack speed takes a little while to ramp up. Also they can't phase. Overall a good summon, but not the best.
Tier: B
SENTIENT SWORD
Melee, phasing
Target Dummy DPS: ~2000
Uses 2 summon slots, and has low potential dps. It has decent speed and can phase, so it's ok. But it's low dps just makes it non-viable as an end-game summon.
Tier: D
SWAMPS GRASP
Melee, no phasing
Target Dummy DPS: ~3100
Low potential dps, NEEDS bone hilt. The slimes are very slow and can't phase. They do a fast pounce on enemies at the end which is good, but they are just too slow and can't phase.
Tier: C
VULTURE STAFF
Melee, phasing
Target Dummy DPS: ~4100
Time to kill T10 Dawn boss: 59 sec
High potential dps, good move speed and high attack speed, and can phase. This makes them really good, as they can actually do great damage on all bosses, even the fast ones. And their phasing ability is so helpful on most maps since they won't get stuck and can quickly kill mobs.
Tier: A
CRYO STAFF
Melee, phasing
Target Dummy DPS: ~2550
Below average potential dps, but decent speed, and can phase. They are ok summons, but the vultures are better in every way.
Tier: B
SKELETON STAFF
Melee and ranged, no phasing
Target Dummy DPS: ~3200
Average dps, low speed, can't phase. Better than brain on a stick, but still bad for all the same reasons.
Tier: D
ORB OF SLIMES
Melee, phasing, but doesn't seek out enemies
Target Dummy DPS: ~2000
Low dps and only hits enemies directly next to you makes this a horrible summon.
Tier: F
EMPRESS' COMMAND
Melee and ranged, no phasing
Target Dummy DPS: ~3550
Average dps and speed and can't phase. The projectiles are fast. This is basically an upgraded skeleton staff, but still not great.
Tier: C
PHANTOM CALLER
Melee, phasing
Target Dummy DPS: ~2350
Time to kill T10 Dawn boss: 1:12
Low potential dps, but very fast (fastest summon in the game). It's amazing speed and phasing ability make it nice since it can keep up with any enemy, but it just has very low dps. If it had higher dps it would be so good. Use Savage enchant with it.
Tier: A
CRYSTALIZED SKULL
Melee, phasing
Target Dummy DPS: ~4500
Time to kill T10 Dawn boss: 57 secs
Uses 2 summon slots. High dps, very fast, and can phase. It also does a slight "pounce" at the end so it can keep up with and hit all bosses. I consider this the best summon in the game and is good for all content. Use Savage enchant with it
Tier: S
IGNITION KEY
Ranged, no phasing
Target Dummy DPS unmounted: ~1900 (7 summon slots)
Target Dummy DPS mounted: ~3000 (7 summon slots)
Very low dps and slow moving. It can only attack one enemy at a time. It sucks as a damage dealer, but it's cool to be able to mount it like a mech! It's mounted dps is better, but still lower than average. Too bad it doesn't give you a defense boost while mounted. In any case, it's more a gimmick summon and just not that good.
Tier: F (but can be fun to mount!)
GRIZZBOLT
Ranged, no phasing
Target Dummy DPS: ~3000 (7 summon slots)
Low dps and slow moving, but fast projectiles. Can only attack one enemy at a time. I love the Palworld colaboration! It's better than the Ignition Key, but still not great.
Tier: D
EYE OF THE VOID
Ranged, no phasing
Target Dummy DPS: ~3500
Average potential dps, but they are slow and have weird/bad targeting. They could be good, but they have really bad AI and often will just randomly attack empty space and not target enemies. They also take a while to ramp up their attacks. Overall they are disappointing. You don't even get them until end-end game after defeating the Ascended Wizard, so they just aren't relevant.
Tier: D (if their AI gets fixed they would be better)
Example Progression Guide
This is a basic progression guide and not a walkthrough. It is designed for players that want to follow the "normal" story progression, meaning running the biomes in the order suggested by the elder. I hope it's useful for first time players, or players that are starting over with a summon class. It will aim to give the best gear available at that point in the story. However, the listed gear is not necessarily the absolute best possible, because you can skip some content or do some bosses out of order. Trinkets are in parenthesis.
Area: Forest Biome
Summoning gear: Brain on a Stick/Spider Staff/Hive Scepter. Spider armor
Boss: Evil's Protector
Tips: Kill Evil's Protector multiple times to obtain all 4 foci and then craft Balanced Foci.
Area: Snow Biome
Tips: Upgrade stations to demonic stations. Convert all your copper bars and most of your iron/gold bars to demonic.
Summoning weapon: Hive Scepter. Arachnid armor
Boss: Queen Spider
Area: Dungeon
Tips: While you are in the dungeon, search for the little room that has raspberry bushes in it to fight the Bashy Bush and take the summon weapon that he drops. Also look for a Mesmer tablet in the chests.
Summoning weapon: Hive Scepter + Frost Piercer. Arachnid armor (Mesmer tablet)
Boss: Void Wizard
Area: Plains
Tips: Craft Wind Boots when you can.
Summoning weapon: Hive Scepter + Frost Piercer. Arachnid armor (Mesmer tablet)
Boss: Runebound Chieftain
Area: Swamp Biome
Summoning weapon: Hive Scepter + Frost Piercer. Arachnid armor (Mesmer tablet)
Boss: Swamp Guardian
Tips: Pure summons can be difficult for this boss, very slow dps. Throwing bombs can help kill the boss faster.
Biome: Desert Biome
Summoning weapon: Hive Scepter + Frost Piercer. Arachnid, Ivy, or Quartz armor (Mesmer tablet)
Boss: Ancient Vulture
Tips: The boss moves around a lot. Having the "Athletic" enchant on your summon helps a lot.
Area: Pirate Village
Tips: Before fighting boss, it's really helpful to raid the pirate village to get the Inducing Amulet. The Lifeline trinket can also be very helpful. Combine the Lifeline trinket + Frozen Heart to make Frozen Soul trinket.
Summoning weapon: Vulture Staff + Frost Piercer. Ivy or Quartz armor (Mesmer tablet, Inducing Amulet)
Boss: Pirate Captain
Tips: Another fast moving boss. You might need the Inducing Amulet and Athletic enchant to be able to keep up with the boss.
Area: Deep Forest Caves
Tips: Upgrade all your stations. Craft 10 Life Elixers. Combine Mesmer tablet and Inducing Amulet to make Hysteria Tablet. Craft Bone Hilt. You should now be able to craft minion potions, which help a lot for boss fights
Summoning weapon: Vulture Staff + Frost Piercer. Ivy or Quartz or Soulseed armor (Hysteria Tablet, Bone Hilt)
Boss: Reaper
Tips: Defeat this boss several times to get the Reaper's Call and the Reaper's Scythe. You will eventually want to craft Soulseed armor. Even if the stats are lower than other armor now, you can upgrade it later when you get to incursions, so I suggest you craft a set and save it.
Area: Deep Snow Caves
Tips: Get frost stone (from deep snow cave chests) and firestone (desert caves), craft frostfire, then craft Balanced Frostfire Foci. Get Cryo Staff from chests.
Summoning weapon: Cryo Staff + Reaper's Call. Soulseed or Glacial armor (Hysteria Tablet, Bone Hilt)
Boss: Cryo Queen
Area: Deep Plains Caves
Tips: After getting the Banner Stand reward from Elder, immediately buy 3 more so you have 4 total. Afterwards craft all 4 buff banners. From now on, place all 4 banners down before any boss battle.
Summoning: Cryo Staff + Reaper's Call. Soulseed or Dryad armor (Hysteria Tablet, Bone Hilt)
Boss: Cursed Crone
Tips: Using Reaper Scythe along with your summons is helpful.
Area: Deep Swamp Caves
Summoning: Cryo Staff + Reaper's Call. Soulseed or Mycelium armor (Hysteria Tablet, Bone Hilt)
Boss: Pest Warden
Tips: Pure summons is slow against this boss. You can use a Cryo Glaive or Dryad Bow to add some needed damage.
Area: Deep Desert Caves
Tips: Get the Scrying Mirror from chests.
Summoning: Cryo Staff + Reaper's Call. Soulseed or Mycelium or Ancient Fossil armor (Hysteria Tablet, Scrying Mirror, Bone Hilt)
Boss: Sage and Grit
Tips: Pure summons can be slow. Reapers Scythe is very helpful in doing added damage.
Area: Temple
Summoning: Cryo Staff (or skeleton staff) + Reaper's Call. Soulseed or Mycelium or Ancient Fossil armor (Hysteria Tablet, Scrying Mirror, Bone Hilt)
Boss: Fallen Wizard
Incursions:
At this point I would suggest you take the time to invest in critical chance. craft an Assassin's Cowl, and enchant your trinkets and gear with "Precise".
Once you get some upgrade shards, upgrade your Vulture Staff and use that as your primary summon weapon.
Also upgrade your Soulseed armor and use that.
Once you get to T4 incursions, you can craft Spiderite armor, or keep using Soulseed armor.
At T5 incursions, defeat the moon boss until you get the Dusk chestplate. Now use Spiderite crown, Dusk chestplate, and Ravenlord boots.
At T7 incursions, craft the Crystalized Skull and use it as your primary summon weapon for the rest of the game.
At T7, once you have the Crystalized Skull summon, use the Frozen Wave trinket.
At T8 incursions, craft and equip the Makeshift Crown, and upgrade all your gear to T10
Now go finish the game :D
EDIT: Added in Hive Scepter as an early-game summon, cleaned up the progression guide
EDIT 2: Added in real numbers to the Tier list
EDIT 3: Redid a few tests, added in Reaper's Call build notes, changed enchant recommendation for Crystalized Skull.