We're not saying there's anything wrong with browsing online Halloween retailers for the perfect store-bought costume, and if we're being honest, going into one of those brick-and-mortar stores that pop up on the corner every year is highly entertaining — but it just isn't really Halloween if you don't make your own costume, right? Maybe it's because it adds the extra nostalgic element to the holiday. Breaking out that sewing kit and going to town on a DIY Halloween costume just really makes…