The most important part of learning ballet is having comfortable shoes. If your shoes are the least bit uncomfortable or poorly fitting, then you will have trouble dancing and learning moves. Even if they seem comfortable, they might have some aspect that makes it more likely to sustain injury to your feet. If you have feet that are usually hard to fit in shoes (if they are especially wide or tall, for example) then you may have trouble searching for the right ballet shoes. But no matter what, you should be diligent until you find the perfect ones.
You should look at the particular shapes that your feet make. The outline of your toes can range from an almost perfect square to very rounded. Your shoes should fit the shape of your toes very well. Some people have a 2nd toe that is longer than their 1st toe. This needs to be accommodated, otherwise you will be uncomfortable in your shoes. There are different things that can be used to modify shoes for particular toes. These include separators, and fitting kits. You can take a regular shoe, and modify it to fit your feet.