i'd suggest a male dwarf flame gourami. It has no chance of outgrowing your tank, its colourful, and as long as your tank is cycled, and you acclimatise the fish properly, you should have no problems
Honey gouramis are great, plus they don't take up much room!
I know they're not gourami but Rams are a good choice, although some people say they are boring, I don't see any difference in character between them and my honeys apart from the rams stick in pairs more.