Please help me

I am in year 9 and have an maths exam in 25 days
These exams are important as they are going to decide what set I'm going to be in year 10 for GCSEs
My teacher told me that the exam isn't on a exam board but has a mixture of different exam boards in it.

Should I do different exams board past papers or not

And also I have a list of topics to revise from
Are there any revision question websites that you guys recommend
Also what should I do after I have done the past papers

Thanks

mathsgenie is good

Don't stress out that much, my maths GCSE is in less than 25 days.