The best thing about attending a costume party is having to dress up like someone else, preferably your comic or movie hero. In a Harry Potter party, you can decide to dress up like Harry Porter, or any of the other characters. There are many places online where you can buy costumes, wigs, contacts, and other accessories that can help you look the part. Obviously, the quality of the costumes, wigs, and contacts matters a great deal, so be sure to shop around for the best products.
Different vendors are going to charge different prices for their products. Since you are looking for the most competitively priced products, be sure to shop around and compare the prices quoted by different vendors. This will enable you to make a decision that is well-informed. Be sure to also check their shipping fees before you decide to make your final decision.