The first thing you have to do is go and take over every planet that you can. You're not going to be doing anything with a 78 unit limit. Use smugglers or C3P0 & R2D2 to look for the easy planets to take. Then move to the harder ones. By the time I did the mission that you are on, I owned almost half the map.
Build mines on any planets with open ground slots. You should also have smugglers stealing from every planet that you don't own (yet
). That should take care of the money problems.