Interesting; I usually do exactly the opposite! I buy one factory on my home planet, then let all other planetary improvements auto build until the colonization phase is over. Instead, I put the military/social/research sliders at 40/20/40. I let the first few colony ships auto build for one or two turns, then purchase them. On the purchase turn, I drop military production to zero, boosting research to 80% for those turns (just have to remember to switch it back afterwards...).
This gives me a colony ship every two to three turns for a good long while because I'm not spending cash on anything else. Grabbing a few lucrative anomalies stretches it out longer, of course. Once I'm out of money, I switch back to 33/33/34 and let it ride there, adjusting my spend rate to keep the cash flow positive. I've got at least four factories on my home planet by then, so I can still crank the colony ships out quickly.
Remember, every planet you colonize is one less planet that you'll have to invade later!
Once I have built enough patrol boats (usually a tiny hull with a single weapon for orbital defense and general saber-rattling purposes) and constructors, I usually go 50/50 on just social production and research for a while to get myself built up.
On all but the smallest planets, I usually build (in order) two factories, a starport, a third factory, an entertainment building, and then a fourth factory. After that, usually a trade building and a lab or two. Before the population maxes out I build at least one farm, too, because I want to keep adding taxpayers.
Putting the factories and econ buildings before the labs seems to work pretty well for me. If I play with tech trading turned off, it doesn't seem to take me too long to catch up with the AI. With trading on, I just act like a galactic EBay. Everything I get from one civ, I trade or sell to all the others, keeping what I develop on my own mostly to myself.
Well, that turned out longer than I thought it would. If you read the whole thing through, I hope you found something useful in it!