It is best to attend coaching classes along with college as coaching classes provide students with well-structured material and exclusive guidance.They hold mock exams regularly, which increases your motivation and competitive spirit. They solve any doubts/problems you have and clear any concepts you might have trouble with. They give advice on how to improve on your weaker areas. So choose a well-reputed coaching institute and it will be worth the investment. 

Good Luck!

If you aim for AIIMS and other competitive exams the coaching is very necessary. 

Do choose the best institute who can guide you the best way with all short cuts and methods in solving the questions in few seconds to a minute.

College alone wouldn't be sufficient enough to give the exam.