My best advice is to take the fun math, whatever that may be. If a class is fun, you learn it properly, so you will be much more able to adapt the concepts and

My best advice is to take the fun math, whatever that may be. If a class is fun, you learn it properly, so you will be much more able to adapt the concepts and strategies to other problem domains. So apart from the mandatory calculus, statistics and linear algebra, as an engineer I took functional analysis, operator algebras, group theory, and intro to hilbert spaces.