I would go with a pair of kribensis and a small shoal of cherry barbs ( 5 or 6 ),,,put a cave in there for the kribs and lots of plants, the barbs serve as excellent dither fish ,,,,,,,,,,by the way kribs are relativly easy to breed and fun to observe protecting their young,,,,,only thing is, you will need another tank for the fry when they get bigger or otherwise risk over stocking the tank,,,,my suggestion is to buy another tank , say a 20 gal,,,put your kribs and barbs in there and then you can use the 12 gal to raise the young until they are approx 1 inch ,,,trhen you have another choice,,,,,sell or trade them to your lfs or buy more tanks,,,,,either way most dwarf cichlids are somewhat east to breed if you have a mating pair,,,so have fun with it and give us an update on what you choose !