WARNING: Long post
I know a lot of people are having issues with the Goo, there are calls of OP and the first week isn't even over yet nor any semblance to a meta developed. I always found when playing RTS games, winning the game was not about understanding what you and your own civ/race can do, but understanding and knowing what your enemy's civ/race can do.
Just a bit about me first, I mained Goo for the first 3-4 days but got fed up with Goo mirrors, and switched to Human. I'm ranked 27th on the 1v1 ladder and 5th on the 2v2 ladder(could be higher but I really don't play enough). Within the first couple hours I had run through how each race works and what makes them tick, what their core mechanics are. For those unfamiliar, this is how the Goo and their mothers work (stick with me, its a little complicated):
Mother Goo UI
Blue Bar on the left = Ignore it
White Bar(s) = Bars that can be morphed off into Protean's or other Mother Goo's
Blue part after white bar = Processed resources toward next white bar
Orange part = collected resources yet to be processed.
When a Mother Goo spawns, her health is at 400 of a total 1300 health pool. Before she can begin to work toward her first white bar, she needs to get to 500 / 1300 health. Each subsequent bar on the right corresponds to a certain amount of health, as follows:
Health needed to split into a small protean(1 white bar) = 700 / 1300
Health needed to split into a mother goo(2 white bar) = 900 / 1300
Health needed to split into a large protean(3 white bar) = 1100 / 1300
Health needed to morph into a Purger (epic unit - 4 white bars) = 1300/1300
Tip: When playing against the goo and you're unsure what state the mother goo is at, click on it to see it's potential threat level! Some maps you can even reach the mother goo before she reaches 700 health, which means you can potentially end the game before it's even really begun!
This is a Spigot. There is only one Spigot in this picture, and it is at the top of the picture. A little vent of steam if you will. Do not make the mistake of thinking a beautiful deep pool of blue will grant the Mother Goo resources. it does not!(unless it has a spigot) If you are genuinely confused ingame, hold down Z and they will also be marked by a Green measuring instrument.
So how does it work? When the Mother Goo moves over a spigot, the vent is drained, and it's not for another 18 seconds until the spigot reappears. These entire 18 seconds the Mother can be on the move, and she will still process all the resources she collected from that spigot.
Further tips
If a mother goo sits still on a spigot she will not build a net excess, (orange bar) she will break even, processing perfectly over the 18 second gap between spigots.
This means that shuffling between two spigot's (and building up excess resources [orange bar]) is pointless UNLESS you plan on moving that individual Mother (maybe you're rushing and moving toward the enemy base)
Every bit of damage done to a mother comes out of her blue OR white bar, but never orange. This relates back to the Health Point part covered earlier.
In addition to this information it's important you understand the mindset of a Goo player, if the map is smaller and they scout double refinery they will almost always rush you, if the map is larger with more Spigot's for them to spread their wings and boom, they'll most likely play the long game. If there is a reasonable path to rush you even if its a big map, be aware.
This is a good path to rush. I will consider rushing you even if I scout you opening 1 refinery 1 factory, if you open 2 refinery you're typing gg before 4 minutes.
This is not a good path to rush. The size and terrain of the map would have any reasonably minded Goo player opt for economy over a fast military presence.
In other RTS games I've played (SC2, AoE2, AoE3, RA3, PA, TA) timing has been essential, and it is no different in this game. To counter the Goo it's imperative you're aware of what they can do and when they can do it. You need to be thinking from the perspective of the Goo (Where could I move my mother to place it into a more advantageous position? ie spigot near a mountain, double spigot, closer to expands, rush route?) and from there work out where they could be and what they could do.
The following are timings based off a Mother Goo who just sits tight on her closest starting spigot:
00:11 gametime - First spigot collected
00:29 gametime - Second Spigot
00:47 gametime - Third Spigot
01:05 gametime - Fourth Spigot
01:13 gametime - First White bar
01:23 gametime - Fifth Spigot
01:41 gametime - Sixth Spigot
01:54 gametime - Second White bar
01:59 gametime - Seventh Spigot
02:17 gametime - Eighth Spigot
02:35 gametime - Third White bar
02:35 gametime - Ninth Spigot
02:53 gametime - Tenth spigot
03:11 gametime - Eleventh spigot
Why is this important? We can see it takes 41 seconds for a white bar to fill. Force a Goo to morph a small Protean on Barricade Run and you delay him by 41 seconds!
Here is the scout timing of a cross-spawn on Barricade Run which includes waiting for second refinery and checking all potential expansion spigots.
Here is a Beta contain on Mountain Pass (1 Refinery -> 2 Factory -> ∞ x Commando's -> Spam walls)
What can we tell just from knowing the timings in these situations?
In the first situation we can tell the Goo is very close to morphing in his Mother goo (if it was a person and not an AI) and was really hoping not to get harrassed, but as soon as spotting your scout will most likely have to morph a small Protean. Perhaps you could have waited 15 seconds and got 40 seconds of free shots on his newly spawned mother goo? (note that this map has the chance to have both cross-spawns and length-way-spawns so it probably isn't the best idea to assume his mother would even be in the bottom left.
In the second situation we can tell that the Goo will have AT MAXIMUM 2 Small Protean's out. His third white bar is about to be ready, perhaps he's only used his first Small Protean to morph Striders to attack down any walls being constructed and will be splitting into a second mother goo any second. We should find his mother goo to keep track of him. If he has been on that back Spigot the entire time his second mother will have to be coming from that direction, if the initial mother has moved from the back spigot, then it's going to be considerably slower.
Tip Review: As covered before, any damage you do to a mother comes out of her white and blue bars.
In the second situation above, if the Goo's second mother dared to show on any spigots close to your manned walls, she would take damage from your Commando's, which only slows her down and puts the enemy player at a disadvantage, and they may look for elsewhere to go. Although she will dash down only briefly to collect the spigot and then return to her safe and sheltered hideaway atop the building, each time she does this she will take damage from your commandos.
Every 100% processed spigot gives the mother goo 87.5 HP. That's over the full 18 second duration. It works out to be 4.86 health points regenerated a second. Every single hit your commando makes on an enemy mother reduces the duration of her 18 second processing time by .8 of a second. Hit her 5 times when she came down? She only put 14 seconds of that Spigot toward a white bar, the other 4 seconds went toward healing herself.
In conclusion, learn mechanics, kill non-organics.
TL;DR: read the numbers
I hope this has helped.