As the topic states the important thing about the Galactic overview is to be constantly doing things and preping...

What I've found is that as the Rebels you REALLY want to move Mon Mothma around from planet to planet when ever you're about to built something... Gt her there, queue it while you get he discount then move her, as long as it stays in the queue then the price wont change, so you move her from planet to planet and build stuff with her discount as much as you can...

Don't leave your ground slots empty, fill them with mining facilities, and if you decided you want to add something to that planet, sell one of the mining facilties and then replace it with what you wanted to add....

Havem't really put much time into the Empire, but I imagine the technique is fairly similar....

The problem with that is that she ain't so protected then.
You don't want a huge imperial fleet coming just as she arrives at a planet.

I prefer to keep Mon Mothma at Yavin 4 and have every type of factory on the ground, and a highest-level space station. Yavin 4 is in a safe rear area, and I just build everything there at a discount then move them where they are needed. I put lots of mining facilities on the planets that produce the most credits, except if they are on the border near Imperial planets.