By “shoots” are you including weddings? Just curious. OP - I’ve been to more weddings than I can remember and I’ve never seen the photographer wearing anything other than a suit or a dress shirt and tie for a man/a dress or nice pants and dressy top for a woman. Dress as you would if you were a guest based on the formality/informality of the occasion and you can’t go wrong. It’s nice to advertise your business but being underdressed in a tacky shirt with logos on it is not the way. Also, you have no way of knowing how many referrals your friend didn’t get because she showed up to someone’s formal wedding looking like she was going to Walmart.