Gryffindor Costume Robe

Waving your wand around the house is a lot of fun, but no one will ever take you seriously as a wizard when you do it without a robe. Look at Harry Potter. He can cast a Patronus Charm so fast it'll make your head spin, and the only thing you've managed to do swatting your wand through the air is nearly knock over your television. The difference? Harry wears a robe.