Emaths has a lot of past SATs papers, ranging across all of the tiers - they're free to download and use. http://www.emaths.co.uk/index.php/4-students/past-papers/ks3-sat-papers They also have a lot of Maths-based materials (following that theme, http://www.mymaths.co.uk/ and http://www.mangahigh.com/en_gb/?localeset=en_gb may also help you with maths-based stuff).
You can also find plenty of relevant information on the BBC BiteSize website - http://www.bbc.co.uk/schools/ks3bitesize/
SAM Learning is also pretty helpful, if your school has accounts set up - https://www.samlearning.com/ There's a bunch of revision materials, past papers, gap fills, and so on that are very helpful.
Those sites also offer GCSE revision help, if you really want to challenge yourself. A target of 7b is very high, but achievable if you don't stress out too much - the average grade for a Year 9 is about a level 5, and the average grade at GCSE is a C, so it's pretty safe to say that you've got the potential to be a higher tier student. I was getting between a level 6b and a level 8a (Maths whizz... my target was a 7b or something like that) in all my subjects in Year 9, and now I'm predicted an A* in every subject - even the one that I was getting the same grade as my little brother in (Religious Studies... ugh)!
If you can't get on those sites, try reading through your exercise books, textbooks, and whatever else you have on hand. Make notes which will help you - highlight key points, draw pictures, write definitions and so on. If you've got questions on a topic (e.g., from an exam paper), look up what the answer is - that'll refresh your memory more than skipping the question.