When dressing for the street, dress appropriate for the weather and the locale. Dress to blend into the crowd, not attract attention to yourself. If you attact attention, you may get more attention than you want.
Everyone wants to dress nice and appropriate for the occasion; however, to be prepared for a possible confrontation, there are some things you should wear, and some things you should not wear.
You should wear fitted clothing that is not so snug that it restricts your movement, or punching or kicking abilities. Clothing should not be so loose that it might it may be grabbed easily and used against you. Clothing should not have anything that could snag on something and hamper your movement. Clothing should not have any parts that could be yanked off and used against you, such as a scarf or cording. Low hanging pants may be in style, but in a self-defense situation, they are a liability. If the opponent pulls them down, it will be very difficult for you to defend yourself with your pants around your ankles.