it really comes down to how desperate you are. however, there should be a limit to your desperation. as an ORM with sub-par to borderline stats, there are only so many schools i can apply to. i'm not applying to schools that don't show love for out-of-staters, schools that predominately recruit URMs, etcetera. if you have stellar stats, then i think 15 schools should do you well. if you've got horrible stats, then applying to every school imaginable is a waste of money and time. you're better off treating yourself to the bahamas.....
just my 2 pennies