Well, at first I didn't. So all my organisation ended up being whatever stationary was on sale in WHSmith as I panicked one school night. For Biology and Physics, I had A5 refill pads, and an A5 folder for each subject, plus an A4 canvas folder-bag thing which held all the notes I was given. I also had an A5 folder per subject for revision.
For Media Studies, I had a single marvel notebook with a sticker on it. That's literally it. Lasted me the entire year, too.
For Maths, I simply used an A4 canvas folder-bag thing, and seperated each topic up with super-cheap presentation files.
Overall, I had three canvas-bag things, five A5 folders (the buggers kept breaking), about thirty super-cheap presentation files (I would seperate science modules using them too), far too many plastic wallets, a marvel notebook, a pack of dividers and so very, very many refill pads (at least 8).
One folder is not enough, but you won't really know what works best for your subject until you get there. Once I realised I needed to have an organisation system, I tried to make it all the same for each subject, and frankly it doesn't work. Each subject will work differently to each other, so you'll need different things for it. If you want to be organised going into the year, my advice would be to buy as much cheap stationary as you can, so it's not awful when you don't use half of it and have to buy more of other things.