Hello, I’m no expert in Illustrator, or shoe design. But if you have an idea in your mind, you just need a tool to shape it. We do not know if you have technical knowledge, nobody asked you, only you crucified. If you have no money, or wishes to hire a teacher, teachers do not have to get angry, if you try to gain knowledge on your own. There are many design programs. The most popular are Illustrator and Photoshop, but not mean they are indispensable. You can start designing with vectors, but if you want to create artistic representations to levels that you will agree, then used Photoshop. I’ve even seen a video of Adidas professional designers, who use airbrush in his sketches.
In the Technique is the art, and vice versa
Greetings.