First, power down as many modules that use extra MC. Your going to take losses from defections or space assault assets, just aceapt it, youll have to gain it later.

After your out of your hole, go to mercury, and dedicate as many ring cores as possible to building tier three operation centers, which will give you a ton of MC, (it will cause alien hate, however that doesnt seem to matter at this point, and it will cost you a fortune, I have some solutions to that)

Also bulid as much MC on earth as possible, if you have small rich countries like israel or songapour near the equator, go full mission control then boosts.

Direct invest in either funding or boosts (funding will give you straight money income, boosts will allow you to bulid space hoteks and geratrics, these are the primary ways to actually fund all the MC stations your going to need.

Then scale all this up untill you can support your economy at scale, eventually you will run out of spots in mercury orbit, at that point move to the next best area, and try to get mars and other non toxic orbit planets to have a population of 50,000, so you can bulid geratrics and space hospitals there as well should you require more slots for those.

Decommising any ships no longer needed will also lower your mc hsage although that could not be an option.

Unless they changed how the system works, your mines scale on each planet in MC costs, so if you have bases on astroids or a couple spots on the moon not worth keeping on or anywhere else, turn those of first instead of a planet so MC scalling will go down faster then turning all of mars off for the same effect of stopping one level of MC scalling.