It's pretty well set up for you to know what to do when, just by the costs involved. The upgrade path just depends on your budget. I concentrated on mech repair and med bay, until I had to pay the big bucks to keep going. Then I worked on morale points a while, then went back when money wasn't a problem.
I filled in the training just to be a completionist. LOL

I'm holding off on what I think is the last mission. I don't know how I'll feel playing the game open ended and I still don't have the assaults I want.

The 2nd to last campaign mission was a PITA! I figured out what to do but didn't have my mech builds right until the 3rd time. Then it went well.
There's a time crunch, a series of target buildings and then a lot of enemies you have to take out. It was pretty satisfying though.