I did some tests with starting colonies, seeing how much money I could wring out of one planet if I didnt care about research or manufacturung etc. As I understand it, the three buildings that provide money (in one way or another), are farms, entertainment centers, and markets. The markets of course give you a direct boost of taxes, the entertainment centers allow you to raise your taxes, and the farms give you more people to tax. However more people also means less morale, so you could almost view farms as anti-entertainment centers, as they have a net decrease in morale. In my tests (I didnt save it, guess I should have), the farms seemed to hurt the amount I could tax more than they added taxes. This may change later as you get more advanced forms of entertainment centers, and stock exchanges which increase morale, but in the early game more people seems to be bad. Unless people do something for you besides give money? Influence hasn't been a problem for me so far, I assume they also increase the influence generated by a planet? If so is it more than the amount an embassy would add?