You are far better off using that cash to buy factories to make colony ships than to directly buy them, you should be reletivly easily able to pump out colony ships every other turn, even every turn if you have some manufacturing bonuses. Just put military spending on 100% and make sure your overall spending is also at 100%. The AI wastes its production on scout ships, so you can almost always outproduce them until they start cheating on higher level
thebelal
I have won every game I play using this strategy, my latest game was a large map with all 9 civs on intelligent. I play as the drath legion without customization for the following reasons. First they start with impulse engines and industrial theory, so you get impulse engines and factories right off the bat. Second they are a good civilization, so you can use all the evil planet bonuses and become neutral without spending any money. Lastly their raacia
the bonuses only work for improvements that actually have production of some kind. So building a captial on a bonus tile is a waste, you won't get any additional bonus for the tile.
I don't know about anyone else, but I have never had a core design be even comparable to a custom one. In fact, I don't think I have made a core ship since my first game. They are just too specific to be useful.
The upgrade optioned are grey'd out because you can't upgrade core ships for whatever reason. You have to design your own ship from scratch using the new ship button, then you can upgrade it. I personally would much rather just tweak the built in ships, I don't want to spend the time making my ships pretty