100% agree with everything already said and no one needs a 9 in GCSE Maths to go anywhere unless you want to do Further Maths as part of a 3 A level study. What I found worked the best when I was helping my friends out with their maths is practice papers. The exam boards always recycle exam questions and more likely than not a majority of the questions of your paper will be similar to questions you've encountered before. You can find tons of exam papers online, on the exam boards website and from your teachers. I would start doing sections of foundation papers untimed, for instance the first 10 questions. Then gradually build up, do them timed, then add more questions, then do the whole paper and so on. Always mark the paper yourself later using a different coloured pen to see where you've gone wrong. Look at the topics you did worse on, and try to look for questions on those at websites like Corbett Maths or in your textbook. Has your school by any chance registered with DrFrostMaths? It's an amazing resource and it's completely free!