1) Keep your morale high, at 100% at least for the beggining. You start with minimal population and minimal economic bonuses, no matter what your tax rate is you are going to get minimal cash from your people. You are better off having your people create more people, rather then cash. Once you have some economic buildings up and some more population (or you go broke and have to) then raise taxes to get some money.
2) On any map where you expect to colonize more than 3 or 4 planets dont buy the colony ships, buy the factories on your homeworld to get colony ships going.
3) Tweak the production sliders so you don't waste a full turns worth of production on something that is almost done. Be carefull however, social project turns to completion is buggy and may need more turns to complete than it shows. I focus on my homeworld, once it is done with its factories and an entertainment network (E network allows me to crank the taxes up to 20 some percent, slowing my cash loss while maintaining max pop growth) I shut off social spening, reduce military spending to exactly what I need to make a colony ship every other turn, and put the rest into researching or savings or whatever (and if you focus social on all your new worlds you get some social spending on them anyway).
4) Probably most important: Redesign a new colony ship! Take off the second colony module, and stick on engines and any support you may need based on map size and density. Try and play a race with Ion Engines (I know Drath have them and custom can get them, also Yor have plenty of engine space on theirs).
Experiment with full/almost empty colony ships, rushing more colony ships out or diverting their slider production to improvements or tech or survey ships.