I like Gal Giv II, but I'm clearly doing something wrong when it comes to the early game economy.  I play primarily small and occasionally tiny maps.  During the initial expansion phase, I kick my economy to 100%, dial my military to zero and have my homeworld buy ships on the cheapest loan plan possible.  I usually get 4-6 colonies with maybe 1 colony ship left over (anymore than that and I just restart, the game is done, which is a pity since I'd like to be able to recover).  

Then I've got the period where I am trying to deal with my loans.  Various strategies here depending on the build I'm using.  But it all sorta plays out the same.  I try to keep expenses down which basically means building nothing except for the stuff you probably should.  And even then, leave a lot of colonies fallow.  Regardless of build, for a while it's just wheel-and-deal selling techs to survive the "negative economy" part.  If I maximize minor races, I can survive and thrive on the highest difficulty level.  But that is super cheaty and isn't fun.  So I got rid of minor races.  Now I can get up to "Crippling" but beyond that, when techs that used to sell for 100+ credits to races with big bank accounts now sell for less than 40 to even the richest customer, I'm done.  I spend a lot of time in a falling behind everyone and then get destroyed by whatever aggressive race decides to kill me.  

I used to use the "Super Diplomat" trait but based on what I've read the real way to do it is the "Super Breeder".  Since I've been using the Super Breeder, which gets me into the chronic debt phase faster (since I'm rocking the 100 happiness 2X growth rate) and (if I can survive it!) out of it a lot faster (more citizens=more tax base).

It gets boring once I survive.  Keep it tight, maybe fight a quick war with a nobody to expand territory then work as an "arms dealer" and sell ships to the losing side of a war to make up for my tech deficit then do like the real rich do and buy land.  Buy land until you've got the map.  Done.

If I want to be aggressive, I can get some military ships early so I can threaten people.  Not a lot of money in that but I can do it.  But then it's all arms dealer,  How do I just be a Dreng and win it like crazy with my military from the beginning?  I just want to fight!