Hey! Good to see you going on to such academic subjects, and I hope I can be of assistance. I currently study Maths, Further Maths, Physics and English Literature
Firstly, decide where you want to be at the end of year 13 NOW. Not necessarily what Unis you wish to apply to, but are you aiming all A*? All C? This will impact greatly how you approach your new school year. I'm going to assume you are aiming for ABB or above, as if you are asking around you are probably pretty smart.
For maths, don't bother with revision guides. The MEI textbooks are pretty good at explaining, and one would hope that you will be doing plenty of past papers! For the sciences (brave you for taking all 3) revision guides seem to be pretty useful.
It is odd that your school is expecting you to purchase all your own textbooks. I got my own maths ones, and only because I like to write and highlight in them. YES THEY ARE WORTH IT. I would buy them second hand. Can I just ask what your school expects you to do if you don't buy them? Just take notes? If cost is an issue, see if you can apply for the 16-19 bursary to help with cost.
I personally base my revision around the textbook and past papers. Past papers will be your best friend. For maths, which I have ended up studying completely independently aside from stats and FM topics, I went through the textbook, did a past paper, textbook, paper, textbook, paper, until I got over 90%. You will find a method that works for you I think.
In terms of "how to get through it" I have 3 main points. Turn up, Do the work, Summarize. Attendance is a good 50% of the work. Homework is another 25%. These two things will be your single best shot at doing well. The thing is, at A Level, the lessons are so dense with content, missing a single lesson will completely throw you and mess you up. Also, Homework is only set for your own benefit. Teachers don't do it because they like marking. Finally, at the beginning, in terms of self study, you can get by until about Christmas with a half hour summary each week per subject. I'm not going to preach about how you should do 25 hours of study a day or something, but definitely do something extra, even if it is just reviewing notes. After Christmas, you'll want to start on past paper questions if you haven't already. Use your study periods effectively for homework, that way you have less to do at home.
Filing! Your proposed system is quite similar to mine, but be wary, some teachers require a folder for their subject to be taken to each lesson,and won't like the one binder option. I personally have 1 lever arch for each subject, then I have a
popper wallet for each lesson with the relevant notes and paperwork that I need. This is a very light way of doing things, and means you don't have to carry a hole punch around with you. However, both methods require you to be on top of your notes, and I've known people to carry around their lever arch files. You will find a method that works for you.
I probably don't need to mention this, but make sure you are prepared for each lesson with relevant materials. Black pen (get used to it for exams!) pencil, ruler, rubber, sharpener, etc. Coloured pens can be useful. You WILL need a scientific calculator, and if your school does Stats options for maths, a graphing calculator is indispensable. Make sure you have extra paper in a ruling width of your choice.
All in all however, have fun! Sixth form is great fun, and while A-Levels are tough, you'll get through OK!