Hello Kelly Bennett,
I like to dress professionally over a layer of conservative workout attire. This way I am prepared for an interview as well as a sample class and for different temperature environments. Do your homework to see what the gym is like and do as the Romans do.
Natalie aka NAPS 2 B Fit.
I expect applicants to dress fitness professionally. They can wear fitness attire, but it should not be dirty, should not be shorts or t-shirts, should not be worn looking or damaged/torn/wrinkled/etc. They should look like they would be the obvious fitness professional on the gym floor, not like they are there to just workout.