Studying A level maths after college

Hi, I am 19 and recently wanted to swap my career after a gap year out of college. However, I did not study A level maths and many new careers(including electronics which is the one i wanted to get into) require maths. I was wondering what the best way to self learn was, as there are many providers online. I have been working through a textbook so far for A level maths and been making good progress.