In 2v2, a forge's main role in my opinion is to supply antiair (sakata MKll), and to support the outpost player. For example, auto-romans as meat shields is a great way to protect your teammate's tanks. You'll need energy if you're forging, so obviously your build needs a generator at some point. Sakata spiders are good to use in SS, but in normal and cold war, missiles and black queens can still beat them pretty easily, BUT, in some situations where your opponent's outpost player is very under pressure, then making spiders can be a good idea. Also, don't put TOO much time or resources into making phantoms, since sakatas will still pwn them too easily. Making a few for pressuring the opponent is fine. That's all I'll tell you for forging.
For capitalist, I think the best thing to use them for is 2v2 outposting. As capitalist, you'll be very strong late game because by then, the resource advantage you'll have will be staggering. Outpost makes the best use of this resource advantage. I don't recommend capitalist for 1v1, since I personally feel that capitalist is relatively less capable of rush countering compared to other governments, but capitalist can still be pretty good.
i usually am cap normally or comm for earthquake. I always make banks first, then go from there, usually forge. get ur teamate to make the opposite. You or your teammate focus on AA(antiair), and whoever isnt go anti-ground.
I've met some people in their twenties and above that play colony, and apparently it's because colony is a strategy game.
And in case you were wondering, no I'm not in my twenties XD
Oh yeah, there's something I forgot to mention. Fascist is a great government to use with forging. Capitalist can work as well, but I personally prefer fascist. There are a few monarchist forge builds, but those are 1v1 rushes mostly.
In my opnion cap is all about being flexible. U shud use it for builds that require both forge and post, because the extra resources are always needed. Fac is good for 1 vs 1 because of speed, and they are also good for forging because of the extra energy, and its ability to make units FAST.