If you upgraded to a 10 or 20 gallon tank, your possibilities are MUCH better than a 5 (really only useful for a single or divided double betta tank) in a 10 you could have an even-tempered betta and a small school of neon or cardinal tetras, or a few ADFs or apple snails, or dozens of other combinations. A 20 is where the options really explode, with the ability to fully utilise tank layers like having surface swimmers (bettas, gouramis, guppies) middle swimmers (tetras, platies, mollies) and bottom feeders (cories, otos, ADFs, shrimp) and give them enough space to really flesh out a complete simulated ecosystem. Live plants are wondeful as well...they look nicer, they function as an ammonia-removal system better than just about any artificial filter, and I swear fish can tell the difference and act happier with live plants rather than silks or plastics