No point buying textbooks but if you want to I can reccomend some. You can't buy a textbook for english since every school has a different syllabus but if you want to, you can find one that suits the things you'll cover in the year for english. For maths there are Cambridge, Insight, and Mathscape.
Agree with D-BOSS,use whatever prescribed English texts your schools studies, as with maths my school always used cambridge for maths, but there are a lot out there. I reckon that you should just get whatever is on your school book list.