I think it's weird how they don't get along... when I was a beginer I put a platy, black skirt tetra, betta, and a neon blue dwarf gourami in the tank and they all lived happily. I had them about 2 years, then my platy died. I still have the betta. The black skirt tetra is in a friend's tank with more black skirt tetras.
Doggfather-Are you sure a dwarf gourami would need a bigger tank? They only get to be 2'' long.
Anyways, not sure what to do in my tank. I don't really like fish that stay on the ground, but I'll look at those fish you're talking about Inchworm. I haven't seen them yet. I think I might just wait a year or two until the betta is gone then add more fish. Or I could put him in a 1-gallon bowl even though I don't reallly like put fish in that small of a house.