Hi, I would advise just getting as much exam practise as possible for maths AND LOOK CLOSELY AT MARK SCHEMES. I say this because you can get lots of method marks despite a wrong final answer and so it's a good way to maximise your marks, even if you do not know how to fully answer a question.
Every time you get a question wrong I would suggest writing out the correct method to answer it from the mark scheme - most of the times this can be used as a template to answer other similar questions from the same topic.
For your mocks just focus on getting marks from questions you are comfortable with or from method marks.
Identify your weaker topics now and focus on revising those first if you feel that is best for you but do not stress too much, these are, I'm guessing, your first set of mocks this school year!
Good revision websites to use are maths genie, maths made easy, revision world, physics and maths tutor.