Bettas won't usually eat flake. There are betta foods out there that they like. I use the Hikari Gold betta food, which seems to be good. They are little pellets, and you only need to feed 2 or 3 each time. They also like frozen bloodworms. Bettas have very small stomachs, about the size of their eyes, so you need to make sure you don't overfeed.
Bettas don't usually like tankmates. Usually you can keep them with ADFs, and sometimes cories or otos. They like it a little warmer than most tropicals. Around 78-80F (26C).