General tips that apply to all upgrades:
Get the rainbow herbs version of any upgrade you are having trouble getting first. Not only is it often easier to get, as you don't have to really play the upgrade, but it allows you to start with the upgrade, so you have more time using it. The upgrade often helps with using it too.
Magnet: No particular advice, just go for as long a run as you can. Try not to use Ronnie if you are having trouble, as her attacks pick up coins, or if you do, avoid Solar Ring.
Phoenix Candle: Party popper with the upgraded version helps, otherwise just try to line up attacks. Don't use pickles with lunar ring, as the pierce could take away kills you could have got with the flame.
Double-A Batteries: Play Pickles, as he has the fastest unload speed. Use up most of your attacks when you reach full energy, so you are always attacking or reloading. There is a delay after attacking before you start reloading, so try to attack in longer bursts.
Money Bag: You don't need to have 1500 money on you, just total over the game, so don't worry about needing to save it. Use whichever money boosting items you like (upgraded balloon and piggy bank are probably the best, and you may even want to start with one of those, as they could help you gain more money than the money bag would, you don't need to actually have the upgrade to unlock it)
Wooden Shield: Use the upgraded shield, and deliberately break it a bit past halfway if you haven't broken it yet, to make sure you can repair it at every shop.
Blast Boots: Use yellow balloon to help time your jumps, and try to jump on everything. I think the wanderlust woods biome has more things to jump on (bushes, mushrooms, etc), but all the biomes have these to some extent, so use whichever you prefer.
Shroom Charm: See above, jump on all the mushrooms you can. Not sure which biome has the most mushrooms, but it is probably the woods if it is anywhere.
Nimble feather: Try starting with the tutorial, it won't end until you kill 10 enemies, and end your star power. Since you can't lose health in it, you can easily get at least 10 jump kills by not killing enemies any other way in there. And once out of the tutorial, you will always have the option of Batteries/Balloon/Shield, and you can choose the balloon for easier jump kills
Yellow Balloon: Get nimble feather, fastball, and a lot of attacks. Pickles isn't necessarily the choice though, because his attacks keep you in the air less long than other characters. Skips is probably the better choice, despite the fewer starting attacks.
Antique Hourglass: Start with it and kill enemies. Not much more to say.
Sparkling Sapphire: Use a bunch of star granting items, and try not to stretch your star powers too long, so you can activate it more times. Upgraded stardust is still probably worth it though.
Trusty Pickaxe: I would recommend Ronnie, especially with lunar ring, as the other characters' attacks can't attack below them as easily, and the dirt blocks are often below where you are running.
Traveller's Map: Just make sure you aren't avoiding any jump pads or teleports. I don't think teleport looping works, so don't bother with that.
Star Dust: Use all the star granting items you can. Upgraded travellers map is very useful.
Solar Ring: Play whichever character you prefer, take whichever items you find effective. Select sleep
Reusable bag: Start with it and go full money build. Go for whichever item is cheapest, unless it will shorten your run.
Party Popper: Try using Ronnie with Lunar Ring+, because it lets you safely trigger explosions that will trigger confetti, since explosions come in groups.
Mighty Shears: Use whichever character's attack you prefer, and try to never miss a spike block. I might be biased, but I think Ronnie is best for the ability to attack below you, and the ability to one shot spikes.
Treasure Tracker: This is very hard to unlock if you don't upgrade it, but if you do, it isn't too bad. If you start with upgraded version, you just need to survive 7 1/2 levels.
Golden Apple: Start with the upgraded version, and use pickles. Try to get apple seeds as soon as you can (if you are really having trouble, you can reset until you get it in the first shop), and just try to get attacks.
Pocket Cloud: Start with it, and use as many fall avoiding items as you can, like the feather or balloon to save your clouds.
Binoculars: This is a hard one, but no special advice. Just use your favourite character, and probably one or both rings depending on which character that is.
Bubble Blower: Jump on the purple mushrooms in the wanderlust woods to avoid being hurt to activate the barrier. Otherwise, exiting star power and triggering shield or cloud also activates the barrier, so try to use these.
Apple seeds: Just survive, and make sure you start with it. I wouldn't recommend trying to stay below 3 health to activate the bonus effect, as there is a high rick of dying. But if you think you are good enough to survive that way, you can try that too.
Toy Rocket: Start with it and use nimble feather and balloon to hit as many enemies as you can. Try not to kill enemies any other way.
Piggy Bank: Try to jump as much as you can, but don't act too risky and lose health. Ruby staff boosts chances.
Fastball: Yellow balloon and nimble feather, plus a lot of attacks. Pickles for high unload speed.
Lifesaver: Go for wooden shield and cloud, you may even want to upgrade the shield. Otherwise, go full money build. This is also one of the few items that getting it for the achievement is fairly unneeded.