The usual answer I’ve received when seeking advice on the mathematical foundation you’d require when beginning a physics undergraduate program goes something like this. Calculus I and II will be your life (this includes differential equations), multivariable and vector calculus will of course take you a long way but this can be learned as you progress through the course, you cannot ever know enough linear algebra and an introduction is certainly useful, complex calculus will be useful for some fringe cases but is not necessary, and a course on probability theory will help with intuition. Of course, all of this comes with a solid foundation in trigonometry, algebra, geometry… the works.

I find that the Mathematics Analysis and Approaches course in the International Baccalaureate is a very complete effort at preparing one for undergraduate physics. In my conversations with others and my experiences of self-studying higher material, the AAHL course does a great job at providing necessary mathematical background. I’ve attached below the syllabus for the course. The AHL sections are for those of you that are willing to go the extra mile. Rest assured, the standard level material covers sufficient mathematics.

Mathematics-Analysis-and-Approaches-Syllabus.pdf

Below are two standard textbooks for the course. The Oxford one is more concise and already assumes that the reader is well-versed with the idea (not the method) of calculus. The Hodder textbook is very illustrative and has more example problems. Rest assured, both are great. For a solid and rigorous foundation in calculus, however, I would direct you to Stewart’s Calculus Series. Any edition does the job. It has long explanations, is very illustrative, and includes more problems than you could possibly do.

https://drive.google.com/file/d/1vGDRKmblhsGMwthF-aK_1ZpkE8QeipPC/view?usp=sharing

https://drive.google.com/file/d/11wdc2wgANOTa3H6Y-5q-PJQzCHKF0cK5/view?usp=sharing

https://drive.google.com/file/d/1KplS7fy-h-ngXHN9oVNGswXlv3zc375s/view?usp=sharing

https://drive.google.com/file/d/1KFTd51YkdCJyD8MpOwIzO-RMriAwwGww/view?usp=sharing

https://drive.google.com/file/d/1B2TJ5K8M8yVE8UbMiU-2YRIwITIQ0kpM/view?usp=sharing