With a school of small fish, I think the next thing to get would be a "center piece fish." This entirely depends on your preference and what kind of fish interests you. Some to consider are a betta, gourami(a powder blue would probably really set off the neons colors
), or paradise fish. You should only keep one of these kinds of fish in your tank. After adding the centerpiece, you should be able to add a bottom feeder or two. Probably an otto would be best, just make sure they have enough to eat in the tank, otherwise you'll have to feed them seperately. Some ghost shrimp would make a nice addition too.
Good luck!
This is all assuming your tank is fully cycled of course.
0 ammonia, nitrites, and nitrate. If you don't have that yet, definitely hold off on getting more fish.