My suggestion is that you get yourself a copy of Cambridge mathematics 4 unit and do the vectors part in the complex numbers chapter.
In order to succeed in 4 unit math you must not only learn how to apply a method (like simply addition of vectors) but you have to understand the method and ways to apply the method than the regular, because when you understand different ways to work with a particular concept you can both apply it to anything as well as think about a problem in a different light.
If you see some of the HSC complex number questions for example you will find that there are the rudimentary questions which ask to find the fifth root of -1 or change z into polar form (mod-arg), then you will find complex number questions that will render you quizzical.