Ask HN: What to study to become a machine learning/ai master?

I dropped out of school a few years ago and have been working as a developer. I plan to start attending school again in the coming fall. My question: what is the best route of study to become a master of all things machine learning? My plan is to go in as a double major for math and computer science as I was before. Which topics in mathematics are most prevalent for machine learning and more specifically neural networks?