Start off strong. Crank your military spending to 100%, and your Govt. spending to 100%, and keep cranking out colony ships from earth every 2 turns. Only load about 100 per ship to keep from stripping Earth's pop too much. In the first 20 turns you'll have 11 colony ships (from earth).
Only colonize 1 planet per system, and work outside in, going further away first. You could have 10 systems colonized within 20 turns, with the 11th ship on it's way. In systems with multiple planets, create colony ships upon initial colonization, otherwise start building constructors. If you're playing on "abundant planets", you may want to pump out colony ships from all newly colonized planets. Keep this up until you run out of planets, or your BC runs negative. This will get you the initial "push" you need to keep ahead in population and economy.
At this point, switch your Govt. spending slider back until you're in the black, and adjust your sliders in tech until it's getting about 45 to 50% of your spending, with social around 30, and military about 20. What you research is up to you, but at this point you should have a solid foothold, and are at this point filling in all your systems with multiple habitable planets.
For an extra push, select for your attributes before you start +15% planet quality. It's 9 out of your 10 points, but you will be able to colonize planets the other races leave alone, and turn normal planets (15+)into class 25+ by the time you have all the upgrades (Soil Enhancement, Habitat Improvement, Terraform, etc..).
I've done this on difficulty up to "intelligent" for all, and I have the Dregin offering me tribute throughout the game to keep me out of their business, which is attacking everyone else. I usually get the offer to snuggle also, and they're set to Pure Evil! So, you know they're afraid of something.
It's all about the intial rush. Get out there strong, and keep building! Don't let those "Snuggly" Dregin get ahead of you, otherwise they'll be dropping by for a HUG!
~SDC~