I think the best starter stuff is a CAA UK Chart 1:500,000, the study material for your exams (if you’re ready and need to do any exams yet) and a checklist for the aeroplane. You can study from all of these while you’re not flying too. I think most young students get headsets for gifts which is nice as it’s convenient to own all your own stuff. My parents bought me a HME 100 from Transair the first year I started training, think it was 2006 and I still fly with that headset to this day. Although don’t feel pressed to get one as most schools have spares to lend out.
Also be aware that you’re only 14 and you can’t do all the elements of the syllabus until you’re 16-17 where you can go solo at 16 and apply for your licence at 17, I would recommend applying this time to your exams too as you get an 18 month window to do them all (except the RT) from when you did the first one. This is just advice so you don’t have to re-site them all before you get your licence etc, at least this was the case when I was a student.