You basically want to earn the maximum amount of cash in the minimum amount of time whilst having something which will be a reasonable backup should the pilot training plan not work out (medical, unable to get a flying job etc.).
If I could go back to when I was 17, I'd seriously consider railway signalling as a career. It's safety-critical shift work, it pays well from day one, there's progression opportunities and a good pension. Merchant Navy is perhaps another good pick, so long as you join directly with a sponsoring company. You could study the theory exams whilst at sea and do the flying during the two-three month blocks at home.