I would first recommend you to start shifting to English. Starting from reading English textbooks for subjects to solving MCQs in medium- English. Next there is no special syllabus or books for AIIMS, you study the same that you study for NEET but with better concept and application. For Physics and Chemistry, I would recommend JEE Mains level MCQs solving and Biology pure NCERT.

Reading textbooks is not the only option but you need to solve MCQs tooon a daily basis. Every month take mock tests to check your speed and time management.