Sir,i want to know if coaching institues are really necessary for IIT JEE preparation?or rather i should find a subject teacher who can help me building my basics concepts in physics n chemistry?

You need help in clearing your doubts and being properly evaluated of your progress.For this you need some one. If you are hard working that you are determined enough to learn all by yourself and you have some one at your disposal who will help clear your doubts and monitor your progress then you don’t eed coaching institutes.