IDK where to start for JEE mains prep as a 10 grade student

I am a 15 yr old whos studying IB rn. I am also planning to clear JEE mains with high rank and get into top NITs But, im basically blank rn. I have few questions :

1. Are there any basic topics I should master before starting proper JEE prep?

2. If I want to prep for JEE , what topics should I focus on first?

I would really appreciate advice (roadmap ?) from people who have done JEE prep especially on what’s essential to cover first and what I can leave for later..

Thanks !!!