Hello, I've finished my IGCSE and I think your subject choice is great! I took English, Math, Phys and Chem. Personally, the best tip is to revise and do every single past paper in the last 5 year or so. I think math is an easy one, just make sure to remember all the concepts and formulae as well as being familiar with the question form. In physics, stay focused on the last chapters since I suppose they are more content-heavy. Chemistry, revise carefully on the reactions and observations. Ensure that you have enough time to fill in the answer sheets! Hope this helps.