According to your foundation. For example, you can't draw at all, so if you want to learn illustration, you must learn the basics of art first! Moreover, this art foundation is rarely taught by oneself, unless the family is really poor, they all sign up for an art class and charge. And because illustrations are all drawn by computers now, you have to learn software! If you can learn by watching online videos, that's fine. If you can't learn, you have to sign up for a class to learn how to operate the software, so this is extra. As for the price, you can ask more companies. Actually, there is not much difference. The key is to choose the training school that suits you according to your own foundation, so that there will be no situation where you can't learn anything with money.