A varied diet is best. A staple food of tropical flakes (or crisps which are new and less likely to cloud water) would be best with some treats in there a few times a week will help keep your fish happy and healthy. Treats could include frozen or freeze-dried bloodworms or brine shrimp, spiralina pellets, or even fresh foods such as zucchini or fresh spinach. Many types of tetras enjoy fresh veggies, but note that they should be removed after a few hours so as not to foul up the water. Frozen foods are a nice dietary supplement, and they're pretty inexpensive and easy to feed as well. Spiralina is a kind of algae that fish enjoy eating. It often times comes mixed with other treats (like frozen brine shrimp with spiralina) or in a wafer or pellet.
Also, be careful about feeding three times a day. You definitely can, but your fish don't need you to. Keep in mind that the more often you feed, the more likely you are to overfeed. Overfeeding leaves uneaten food in the bottom of your tank. This rotting food can throw your water quality levels out of whack allowing illnesses or other issues (algae growth, ammonia spikes, etc.) to take hold in your tank or even killing your fish. Ammo spikes are going to be particularly hard on your neon tetras. If you want to stick to three times a day, feed like half a pinch, tops, Or you can net out uneaten food after feeding. Otherwise I would feed once, maybe twice daily. Since your fish are all small, I would go with only once.
Good luck.