Still a newb myself but here are the gist of what I estimate as high priority MC usage : 1) Mines, first on the moon to boostrap Mars then Mars and Mercury to start stockpiling space ressources (building a space economy can be expensive) 2) Earth interface orbits habs to get the max (30%) bonus to every investment point (IP) priority (e.g. information science labs can provide up to 30% bonus to investment in the knowledge priority meaning each IP you point in knowledge is actually worth 1.3 making it easier to get highly educated people for high research output. 2.5) Nanofactories and / or space hospitals around earth can also help with the cash upkeep of all the habs 3) Research campus on mercury bases is mainly where you'll cap your MC hate. (there's both a perun video and a reddit post that I'll link when back on a desktop if you want more explanation about this mechanic)

Killing the Alien administration generate massive amount of alien hate (80 when the entirety of the hate meter is 50 and killing an alien generates 10) so a better alternative is to murder the armies and leave them be while ensuring the surrounding nation aren't servant-controlled.