That's a first for me. I've only ever heard people say 6. Never 3. I would say at the very least 6. Preferably 8-10.
- Some guppies may be compatible with some bettas. The problem with them is that the colour and flowing fins can make them targets for bettas. I wouldn't do them together personally.
- Glowlight tetras should be compatible.
- Black neons should be too.
- Neon tetra are not generally recommended - caridinals fit in better with bettas due to temperature.
-
White cloud minnows like colder water than bettas. Wouldn't do them together.
- KuhlI loaches - just fine.
- Hillstream loach - generally prefer cooler water than bettas.
- Rainbowfish - may work. May not. They may nip the betta or cause him stress. Or not.
- Corys should be just fine.
- Cherry shrimp may very well be eaten.
Ideally there would be at least 6 of each schooling fish. In a 10 gallon, I would not add anymore fish. If you upgrade you can up their numbers if the tank is of suitable size. Otherwise I would maybe consider rehoming some. This is a lot of fish and a lot of activity for bettas. I can see one becoming aggressive and stressed due to it all.