Math is a huge field and I'm not sure any can truly have both a deep and wide understanding of everything in math. But if you want to give it a go, why not sta

Math is a huge field and I'm not sure any can truly have both a deep and wide understanding of everything in math. But if you want to give it a go, why not start with the tried and tested "Euclid's Elements" and a book on the history and philosophy of mathematics. If you are still interested, then tackle a course plan laid out by MIT or any other reputable university. Also, I suggest getting an exercises/solutions book because math is doing. You can read the theorems, corollaries, etc and think you understand it but until you try to solve a problem yourself, you really won't know if you really understood the topic. And in your down time, you can check out math related channels/videos on youtube or elsewhere. It's going to take a lot grit and determination. Best of luck to you.