Hii

Firstly, its too early for you to prepare for MBA. But Looking at your confidence to prepare for MBA in Class 12th is quite impressive. For getting admission in Top College in MBA Course. You need to give Entrance Exams Like- CAT,MAT,XAT etc. in the last semester of your college. I would suggust you to strong your basics of Math, English because these are the most important sections in any MBA Exam. You can strong your basics then it will be quite easy for you to study other sections.

All the best.