I do not use extra speed or rush buying of ships. I will post the basic strategy here, it will also be included in my report which I will make a separate thread for.
Game settings: Tiny map, otherwise default. 1 opponent, set to incredible. Relations are set to 'at war' and will not change, i.e. I refuse any peace offers. It is far too easy to exploit the AI otherwise.
Custom Race: +30 economy, +50 military production, 1 point left over, I tend to pick luck. Political party Federalists for a total of +50 economy. Techs: Hyperdrive, New prop techniques, ion drive, xeno engineering, xeno research.
Strategy:
Turn 1:Immediately buy a xeno lab, set spending and research to 100%, taxes to 49%, begin researching Impulse Drive. It should be done in 3 weeks. Set flagship to auto-survey and send initial colony towards the nearest system that will increase your range.
Turn 2: Buy factory.
Turn 3: Buy factory.
Turn 4: Impulse drive is done, you should be able to design a colony ship with an effective speed of 7 (no support) or 6 (with support). Create both variants.
Set military production to 100% and start building the longer ranged version. It should be done in 2 weeks (this is why we take the +50 mil ability).
Turn 5: Hope that you managed to get a good nearby planet with your initial colony, if not, keep it moving, it has plenty of range. Also hope that your flagship found some money. This is not vital but makes things easier later.
Turn 6: Send your new colony ship to the nearest star to the enemy homeworld. Depending on luck and starting positions you may get there in time. Note: if you see a really good planet (15+) along the way, grab it, but otherwise keep going. At this point you should have around 3700BC and be losing 35 or so per turn. You can keep pumping colony ships for quite a while.
Turns 7+: Keep sending your fast colony ships to unclaimed stars and look for habitable planets. Since you are producing 1 every 2 turns it will be very quick. Take planets near the enemy and backfill. Prioritize high quality worlds. If you see economic resources design and build a fast constructor to take them. The other resources are not crucial at first. Try to restrict the AI to 3 to 4 worlds. This is possible but requires luck. More likely they will get 5. Most should be shit though.
When you have colonised all you can, set social spending to 100%. Specialise worlds, but focus on economic improvements with a few dedicated research planets. When your treasury gets low, switch to 100% research and get economic + military techs - you will need them - the comp, even with 4 worlds to your 9-12 will still outproduce you at first. With the huge advantage you have from the landgrab, though, it is pretty easy to win from this point.
The economic bonus means that you will be able to keep spending high. This is essential. Try this strategy and I garuntee that with a little practice anyone can beat incrdible/suicidal