1) Habitats (we gotta live)
2) Energy (this will cover fuel, heating, automation, defence)
3) Mining (this gets us the resources to do all the above)
You corner the market in any of those three and you will be set for the imaginable future.
Why exactly do we need to live in space at all? Can't we send more or less autonomous spacecraft to retrieve the resources, and stay safely here on Earth?
I mean - we extract oil from under the sea without having to move to underwater habitats, don't we?
I guess what I'm saying is that robots can identify problem points, but at the current time can't actually troubleshoot or resolve those problems. Those are really difficult problems to solve.