I found that the best way to start is to cross breed a few times between your starting fish, and find the best combination.  In my first set, I was able to get 2 pink goldbulbs, and two orange goldbulbs, so I kept breeding and selling these, and focused exclusively on getting my environment fully upgraded.  After that it was easy to keep fish.
I also started two grids.  Once tracked the fintype, and one tracked the fishtype.  I also kept an eye out for valuable fish.  The canary fire-arrow is a cash cow.  Once i got this, I bred and sold it like crazy.  That made me rich.