For what it’s worth, over approx 50hrs in-mission time has given me 2400 super credits. Enough for the first premium warbond, this new one, and 450 left over which I’ll put towards the second one. You seriously don’t have to spend a dime in this game.
I’ve grinded some credits for maybe 4 hours and just played the game. Got 2500 credits left, both battle passes and 2 armors with helmets from the superstore.
Just start a trivial mission, go to all points of interest (usually 8 to 13) and after last poi just leave to ship. Rinse and repeat. The best missions are the ones without a bug objective, so raise flag or activate pumps. Bot missions are also good. Pick a map without debuffs and good vision. I recon you can get 300+ super credits per hour.