So at this point from trolling the huge REDDIT forum, dont buy ships.
On any given planet, look for the orange beacons.
craft and use a chip to use the beacon
Search for communications
Search or keep searching until you get communications tower.
Fly to the tower and solve the riddle (usually math related, and pretty obvious, worst case its 1 in 3 to guess it right and if not reload)
Get the location for a crashed ship.
Crashed ships are almost always +1 storage unit over what you have now.. find the ship, repair the pulse drive and launch ONLY to be able to fly it.
Rinse and repeat.
Regarding upgrades.. unbelievably, you CANNOT move over upgrades, and will have whatever the other ship has by default. That said, as you investigate wrecked ships, you can get the warp drive improvements without having to build them if it has it already. Being unable to move upgrades from your ship, or the multitool either as well, is insane.
I have like a like a 26 or 26 slot ship now just by doing that. Granted, very slow, but I hear the max 48 slot ships are over 100mil credits.