If he or she is going to make how you dress more important than who you are. They are NOT for you. Sure it's important to be clean not dirty, fresh not stinky, appropriate not off putting. But iot even more important how you treat people, how you react under stress, how you gently handle problem people and situations.
If you are judged as not good enough because you wore socks with your sandles. Move on. She or he is not looking past the surface.