The clothing patterns you buy at a sewing shop or walmart, generally cover a range. After you open the pattern up, you cut the lines that correspond to the size you want. You don't necessarily need to take a sewing class, but it will definitely help. You could just buy the cheaper patterns and practice with them. The common pattern brand at Walmart has decent instructions for beginners, and are really designed for beginners, so not too complicated. I think the brand is called Simplicity.