How to get glue off rhinestones?

It depends on the type of glue that has been used. If it is super glue, of course acetone will remove it. If it is hot melt glue, a little heat will take care of the problem. If you used some of the more recent glues, check the package directions.

I would try the acetone (finger nail polish remover) first as this disolves most modern glues. Be sure to rinse your rhinestones immediately as acetone will mar the finish of the stones. If they are plastic, as most stones are today, it's best to just get more because it is not cost effective to recycle this type of plastic. Test on one small one first before you do them all.