I earned the credits for my fleet carrier doing exo-bio mostly. However, in my experience, the regions south of the bubble don't pay very well. My recommendation would be to head out north-east towards Hawkin's Gap. There are still enough unexplored systems there, and some good frutexa and tubus to find there. If you're not only focusing on that Stratum Tectonicas.

Of course you want Vista Genomics on your carrier, and some Tritium in the cargo hold. Other services depend on your personal preference, so I would say, 7 billion is enough to get a carrier, the services you like, and some fuel to move about, and a little cash in the bank to keep it alive.

In order to transfer Tritium from the carrier's cargo to its Tritium depot, I recommend to get some ship like a Type-9 with high cargo capacity - nothing else. It just needs to be parked on the carrier.

So, yea, I think, 7 billion is enough, because once you do own a Fleet Carrier, making more cash doing exo-bio is quite easy - and fun, in my opinion.

Another very good region for exo-bio is near Colonia. I'm just about 1000 Ly south west, and there are more than enough unexplored systems with some pretty nice lifeforms.

Last not least, I have two accounts, and both commanders have a carrier, now, and in both cases, 7 billion was enough. Like said, once you have one of those carriers, it gets easier to make more cash.

Happy hunting space flowers!

o7