For an interview you must be formal clothes.
I would suggest formal/casual you want to still be able to move comfortably if they offer a trial shift.
Answered - Waitress and Back of house (Former Employee) - Bridge Street, Taunton, UK
Answered - Restaurant Manager (Current Employee) - Wrexham, Wrexham
I found it's best to wear formal clothes to any interview as you want to set a good impression.
Answered - Chef (Former Employee) - Newcastle upon Tyne, Tyne and Wear