There a number of options. :)
The Sorority - 5 female bettas, a colony of shrimp OR a snail.
The Livebearer tank - a betta of either gender and 3 male guppies OR platies OR 4 male Endlers (Endlers are a better choice, as they are smaller and the males are very calm)
Tetra tank - a betta of either gender and 6 ember tetras (neons work too, but embers are much better)
The cory tank - 1 betta and 4 normal cories OR 6 panda cories OR 8 pygmy cories
Inverts - 1 betta and a colony of shrimps!
Live plants are always great, and there are some easy starter ones, such as anacharis/elodea, java fern, java moss, ambulia, anubias, cabomba and lacefern. :)