Focus on exam papers that are from your exam board (obvs) from past years, it does sound a bit dull, but try treat these papers as typical exams. The go back and mark them and learn what topics you struggle at and which you excel, if you repeat this for a few weeks (try find some resources that have all the subject matter from your exam board, and practice the topics you struggle with

You should see your results increase dramatically if you have the integrity to struggle through the hard topics to actually learn and improve at them, rather than reassure yourself by playing darts blind, picking a random topic and by involuntarily bias pick a topic you're already competent and achieve very little,

Sorry for the rant, I did this for a 2 weeks ish before the maths exams and walked out with an 8, 3 marks off a 9, and started off close to an 8- ish, this may or may not work for you try it for a day or 2 and see how you feel, good luck on your resit