Just under 3 months until the first exam. I've more or less failed the mocks. What can I realistically achieve?

It's been a year of procrastination and low attendance. I've already failed AS last year. What is the best course of action here to get the highest grade possible at this point? I.e. most effective way to revise and maintain discipline? I'm doing physics, maths, chemistry, biology... I timetabled my whole week in an Excel file to see how much time I actually use and how much I could use. The answer is - a lot more. I don't think I need motivation, I feel like I'd be genuinely sick if I come into the exam room not knowing the material. I'm just wondering what's the technique for the highest achievement per unit time.