you mentioned glowlights somewhere, they are a good fish to breed. Most of the common tetras are relatively easy, as are most of the barbs, danios etc. From the ones in your signature, try the glowlights and head-and-tail-lights first, then the neons as a practice fish for the cardinals. Neons are actually dead easy to breed, you just need to have the tank darkened for the eggs and fry. The procedure is similar for cardinals, but they are more reluctant breeders.