When performing, you need to be comfortable, but you also need to stand out. Some of the street performers I've seen have said that it doesn't matter to them what they look like on the street since it is the street. These are people that just want to be like the people around them. I disagree with that thinking. It doesn't matter where you're performing. You are the performer. Dress like one. That doesn't mean a magician should wear top hat and tails on the street. (It's debatable how many magicians should wear top hat and tails on stage anyway.) You should wear something appropriate for the street, but you most definitely should not blend in. Most importantly, if you don't want to be treated like a beggar, don't play the starving artist role by looking poor. Spend money on a good costume. People pay for what they see. They remember you more for each thing you do. How you dress is part of it.