I agree with Brad.
20 gallon long (30") would be best for platy's. They are a decent sized fish and reproduce fast.
10 gallon tanks are, in my opinion, poor sized tanks for most fish.
Neon tetra.
Ember tetra.
Amber tetra.
Celestial Pearl Danio
Chili Rasbora
Dwarf Rasbora
Emerald Dwarf Rasbora
These are better options.