You are going to want to start off with at least 10 cherry shrimp. Also because fire shrimp are so cheap now you might want to start off with those instead. They are just as hardy and better looking IMO. Neon tetras might not be best with the shrimp. I have had neons and cardinals with shrimps and once they were removed from the tank the shrimp came out a lot more. You might want to look into some small nano fish: Dario Dario, CPD, Chili Rasboras. A school of neon tetras would be a bit much for such a small tank.