Your game sounds rather touch and go. Hope you pull it off. I find Xcom to be far more satisfying at times than i even find Civ. Especially when you snatch victory from the jaws of defeat. That doesnt happen very often in civ. You usually just run away with it. Whereas its standard fare in xcom.
Yeah, it was close, but I pulled it off w/ an August win. I had a really small roster as many of my up and coming backup troops got killed. In the end, I had just six colonels, one of whom got within one health bar of dying in the penultimate mission. My team for the final mission was two rangers, two snipers, a support, and a grenadier. I would have rather had two grenadiers and one sniper, but it worked out fine.
Base Building
Someone mentioned wanting some tips for base building. Here's my strategy.
As far as I can tell, you always start in a corner on the first row. If start in the middle, this may require some adjustment (or not). For the purposes of this, I am going to assume the upper left corner starts open, if it is upper right then just mirror the system. There seems to always be two power spaces, both located on the lower two rows.
I start with a workshop in the open space. The workshop lets you staff an engineer who can then supply two gremlins to staff orthogonally adjacent rooms. An upgrade to the workshops lets you staff a second engineer for two more gremlins. Without an engineer, the workshop is useless so getting an engineer is a top priority.
Once you have an engineer, use him to build and staff the workshop then use the gremlins to start digging out the two adjacent rooms. Once they are dug out, build an AWC in the top floor opening and a power coupling in the other. Use your second engineer to clear out the last room on the top floor. Once that is, build the GTS in that space. Clear out the remaining rooms in the second floor, starting with the one under the GTS. I like to put the Proving Grounds on the right column of the second floor, under the GTS. Once the middle one is cleared, I will demolish the first workshop and rebuild it under the AWC. Upgrade that and staff it with two engineers and you can easily staff the AWC, Proving Grounds, power coupling, and use a gremlin to dig out the floor under the second workshop. This gives you four gremlins to staff the AWC, power coupling (you'll want two there eventually), Proving Grounds, and whatever is under the second workshop.
Priorities from there include resistance communications, the psi lab, and the Shadow Chamber. I like building the Shadow Chamber over a power chamber and using the second power chamber for another power coupling.
This base building strategy allows you to double up on your engineers early on, which is pretty valuable in base building. You can get your base up and running much more quickly by leveraging the workshop. It also allows for a fair amount of flexibility early on as you don't necessarily need to staff the power coupling and AWC so once you have those up you can pull the engineer from the first workshop and reassign him.
However, there are a few weaknesses as well. This strategy is costly, not just in terms of workshop initial costs, but also in upkeep for the workshop. I often get the low income warning when doing this. It also delays the GTS for a bit longer. You probably wouldn't have a unit w/ a high enough rank to unlock squad size five until a few days before the GTS is done so you might have to do a mission or two w/ four instead of five units. Not that big a deal. Finally, this strategy does delay resistance comms a bit. If that's an issue, just replace the Proving Grounds w/ a resistance comms and Bob's your uncle.
If you happen to land on a continent w/ the "fire when ready" bonus, you may want to move the Proving Grounds away from the second workshop as well, probably replacing it w/ resistance comms. An engineer is still useful for the Proving Grounds for armor and other projects, but if you have fire when ready you may not need an engineer there full time.
A key takeaway here is that you do not want to wait until you've drilled down to the power blocks to put up power couplings. Your base can only run two or three facilities w/o a power coupling. It is tempting to drill down to the power blocks first prior to building a power coupling, but in the end it isn't worthwhile b/c it delays your building so much.