Hello please I need guidance

Hello , fellow seniors I am joining vit chennai cse( AI & ML) and after that I wanna really full fill my dream of getting in good college like iit or nit or bits pilani . How to start preparing for gate and from which year anyone who is preparing or successed can advice me. If you have cleared bits pilani higher degree program pleaseee advice me I really wanna full fill my dream to bits pilani goa campus.