hey,
my advice is definitely buy 3 folders and a notebook. you're definitely going to need basic stationery and a scientific calculator. Maybe have a separate folder for each piece of coursework if you have to do it, it's easier, Maybe get a packet of highlighters so you have it when you need it in studying and in class and maybe sign up to a free quizlet account as it's extremely helpful. a clear pencil case is necessary as well as a black pen.
Make sure you have a pencil case and a bag you like as it's easier when you see it in the mornings if you hate school everyday and sure it's a big and strong bag as each folder and each book gets extremely heavy. Maybe have a seperate folder for creating any notes as well as seperate sheets at school, a simle small one will suffice.
Maybe get some flashcards and paper to create study notes along the way as it's easier as well as extremely effective.
even if it seems a lot, it isn't and everything you can do is your best, good luck in sixth form!