My first couple of games were like that, would trade all my tech for money to research more tech. Found that to be a very bad cycle if some of the AI manage to kill off 2-3 empires or they all go broke just when you badly need cash. Just didn't see how my empire would ever make enough money to support itself.
In my latest game, I put the tech to far better use, buying starbases from my opponents, then loading them with cultural enhancements. I also give enough away that I've never been in a war, but I'm always prepared for one (150-170 military rating). Some poor civ comes crying to me about being beat up on and I just give them 4-5 of my weakest ship class. That makes them like you, and helps keep slow down an overly agressive AI civ.
When things get going fairly well after the first 1/4 of the game or so I crank down the tax rate as low as I can to ramp up my population growth, then crank it back up when I run low of money. I keep moving it up, maxing my tax revenue, that keeps my population from going so high in the mid to end game stage that I have serious morale problems.
Since I've been making everyone like me I tend to get a more than fair proportion of the trade income.
On the last turn of my latest game (all AI set to normal, gigantic galaxy), I was getting 50% of the trade income, and my 1169b population was cranking out 9014 in taxes at a 60% tax rate, my approval rating was 61%.
~SDC~