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.