This advice is for when you are like in year 11.But as you enter year 11,end of year 10 start doing the maths 5 a day questions by Corbett maths daily.Near the end of year 11(like Christmas time to summer term) start doing aiming for grade 9(or whatever grade) papers on my math cloud.Apart from that rn in year 9,try to make sure you properly grasp topics like ratios,algebra and surds+indicies. MATHS IS ALL ABT PRACTICE. Always remember that if you struggle on a topic.Work hard to understand the topic by watching vids on gcse maths tutor(he also has amazing gcse resources) and then work up to the hardest Q's which he does in his vids.And also please try to enjoy year 9 as much as possible;it gets a lot harder from there.Ik this is unrelated but I want as many people to know abt these resources.
best of luck,
from a year 12 taking bio,chem and maths who got a grade 9 in maths gcse and had to work hard to get there.