A m/f pair of bettas is a bad mix. The males will often kill the female with too much attention. A single male betta or 3-4 females will be fine, but mixing genders should only be done for spawning. Suitable tankmates for bettas include non-nippy fish that lack the large fins of the male betta, cories, most pleco type fish, snails, shrimp, and ADF--if you're willing to make sure the frogs get enough to eat. A nice setup would be a planted 10 with a male betta, 5-6 pygmy cories, and some amano shrimp.