This is a discussion on Betta Compatibility within the Anabantids forums, part of the Freshwater and Tropical Fish category; -->
I plan to make a community aquarium basically pet shop's here don't sell female betta fishes, so I wanted at least one betta fish ...
Tiger barb aren't a good idea to keep with betta, even in larger groups. They are notorious nippers, and betta's long fins would just be irresistible. Some of the smaller tetra like ember tetra, harlequin rasbora, pristella tetra or catfish like oto catfish, cory cats, and bristlenose pleco are a much better idea. Mollies might work, too, but male guppies are too vibrant and will often become the target of male betta aggression. Alternatively you could just buy a 5 gal tank for your betta and build another tank around tiger barbs.
If you're talking a male Betta, it should be on its own. This is not a "community" fish. First there is the issue of the Betta being aggressive to other fish, and it will often eat smaller fish [I had one that ate neons]. Second there is the reverse, where other fish will frequently view the Betta as a target. Some fish are more prone to this than others, but even normally "peaceful" tetra can become very nippy when faced with temptation like a Betta.
Even if no actual physical interaction occurs, the fish are "thinking" such and the other fish can read these chemical signals, what we term pheromones and allomones. It simply is not wise to subject fish to this.