IMHO you should never breed pet store Bettas, there are enough pet store quality fish sitting in cups everywhere, plus you don't know the genetic history of the fish. Pet store suppliers jumble up the genetics of the fish to produce quantity, not quality, so it prevents you from ever achieving a goal. Delta tails aren't exactly in-demand, although breeding halfmoons will render plenty of them, you should still aim for halfmoons or HMPK to begin with. You can sell higher quality Bettas to other breeders and owners, and trust me when I say there are plenty of them, so long as they are decent quality.
As for tips, do plenty of research and ask lots of questions. Do NOT try breeding out of impatience- make sure you are 100% prepared. It's also important to find experienced breeders who are willing to walk you through things. I'd be happy to help, I'm experienced and I love helping people learn about this hobby. My email is email@example.com
if you'd like to contact me. You also need to understand the basics of betta genetics, which I can also help you with.
It's confusing, challenging, expensive and time consuming. However, it's also very rewarding, potentially profitable and teaches you many lessons about patience.