Numerous costumes is a logistical nightmare, find yourself an assistant.
Unnecessary changes of costumes for one actor is fraught with problems
If you don't have transport, get your performers to bring their costume each day, make them a list of what they are meant to be wearing.
Costume is always important, even if its just a class in school uniforms, consider the artistic element in every choice you make.
Any time you talk about the look of the film, it's not just the director and the director of photography. You have to include the costume designer and the production designer - Spike Lee