Linear algebra
If you don’t have much formal training in maths or programming it can be daunting to start with linear algebra. During my PhD I started several online courses but struggled to build intuitions because, to be honest, many courses are not that great. Here is selection of tutorials, videos and courses that I found incredibly useful.
3Blue1Brown - essence of linear algebra
This beautiful youtube lecture series by 3Blue1Brown is really insightful and is both a great introduction as well as a refresher. It has beautiful visualisations and individual lectures only take between 5 and 15 minutes to watch.
Mike X Cohen - complete linear algebra
When I stumbled across this Udemy course I was initially reluctant to pay for it. I am, however, really happy that I did. Mike is a great teacher and uses code to make mathematical concepts very insightful.
Deisenroth MP, Faisal AA & Ong CS - Mathematics for machine learning
This excellent book is a great introduction to many of the (mathematical) concepts important for machine learning.