What the f*** are you doing with all your money? Skill training should only be like 10%-20% of your expenses at most. Where's the other 80 to 90 percent going? You're doing something very, VERY wrong here.
Don't listen to this guy. Skill buying shouldn't even put a dent in your money. I'm saying that as someone constantly spamming crew skills, buying every skill available, best ship upgrades available for my level at the vendor and just generally letting my money burn a hole in my pocket. I don't buy gear though. You get more than enough gear from commendations, loot and mission rewards.
Edit: And always do your bonus objectives when it's one of the multiple part kind. Those always give blues, oranges with blue mods or 3+ commendations.