I would suggest having 4-5 females (more is better) on one side with 4-5 cories, and the male betta on the other side with 2 ADFs. Of course, do heaps of research on ADFs first, because as Mo has pointed out, they don't have the same care requirements as fish. :)
I would skip out on the apple snail altogether. Messy, quite boring, and they have creepy...erm...man parts.
Make sure you find out what sort of cory you have. It is important to have all the same species.
I strongly suggest doing a heck of a lot of research before attempting breeding. I also wouldn't breed petshop bettas - you'll be creating "mutt" bettas and they will be harder to rehome, plus you won't be adding anything positive to the species in terms of genetics. Casual breeding with bettas I would not advise.