Competition for JEE Mains is tough nowadays. So if you are planning to self study for JEE Mains then you have to work even more harder. Anything is possible but you should be determined about it. If you join any classes then you would be able to clear all your doubts. If you self study then you have to clear doubts by yourself. So it totally depends upon you. 

For now on start studying NCERT textbooks both of 11th and 12th standard. Solve questions from them. Refer reference books. 

HC Verma for Physics is best as it explains concepts very well and there are many problems to solve. For chemistry Chemical Calculations by R. C. Mukherjee is also good. 

For mathematics you can refer RD Sharma.

There are many other books available for JEE Mains. Note that there are many other books available for JEE Mains. Just see to it whichever book you read and solve you are thorough with it. 

Also solve past years papers .It helps a lot to score good. Set time limit and then solve. It will help you analyse your speed. 

If you still have any queries feel free to ask in the comment section down below.