My school gave everyone an account for this site called mathswatch and its SO HELPFUL it goes through EVERY.SINGLE. TOPIC. in small clips and they're all numbered and graded so easy to find. I'm in year 11 so I'm not sure if they have updated things for the new GCSEs - they probably have. The downside is that I think your school needs to make an account. You could ask your teachers I'm sure they would be happy to if you don't already have one. But seriously it has helped me so much. Whenever I don't understand anything I go straight to that and find the topic and it explains it in 5 minutes with some extra practice questions - they even have worksheets (which my teacher gives for homework). Anyways, my target was a B but then it became A now my teachers are hoping for an A* out of me so it works and DON'T STOP DOING PAST PAPERS.
But most importantly,
RELAX, it's great that your starting now but do it bit by bit and don't get worried so early on it'll just add to the stress next year.
hope that helped