If you are to have cory cats with the Betta in a 10 gallon, that's pretty much close to the max. You don't want to have to add a second filter, causing more issues for the Betta. Plus cory cats would much rather have more space!
How long has the tank been running?
Is it cycled?
Is it heated?
The thing with mollies as well, is that they are brackish water. In stores they are stupid enough to keep them in fresh water... Which is one of the leading causes of columnaris (mouth fungus) in mollies and balloon mollies.
Instead... Why not go with the Betta, platys or tetras (3 should do, one male to two females or all females) and shrimp? It's an even distribution, won't kill the cycle, and most importantly can keep the fish happy. Just make sure to quarantine the platys befor putting the Betta into the 10 gallon (quarantine 2-4 weeks). This stops infection or diseases from spreading.
*** I will say no to neon tetras, since I know that someone will mention it. They are a schooling fish... And do best in large numbers. They also prefer more space as they are active, just like danios.