In my 10 gal
I keep 1 male betta, a dozen red cherry shrimp, and am planning on adding a school of neons. A betta should get along with any small fish that don't have flowing fins (no guppies). Also, you will want to avoid nippy fish as they will pick on the betta. Along with neons, you might like harlequin rasboras or celestial pearl danios.
edit:that //along with// should have been instead of