If you are mentally prepared to study for 2 years continuously and more importantly consistently, clearing all your doubts and solving all varieties of questions that can be asked then there is no problem in studying on your own for Mains. Coaching is required but not necessary to score good in JEE mains. Coaching is required in the sense you need to study consistently, they can guide you and for day to day basis study. One significant advantage is to prepare in a right way as for any competitive exam quantitative studying is not necessary, qualitative studying is required. Day to day basis advanced questions practicing can be provided by coaching institutes. Take mock tests that are organised by the institute seriously that would be helpful to get general knowledge and understanding of the exam. But most importantly study seriously and understanding of whole syllabus is mostly important.

All the best.