Dear Gagan,

JEE Main preparation is helpful for MHT CET as well, as according to the new change MHT CET level is raised to JEE Main.

JEE Main level is higher then all the other exams of engineering. If you are well prepared for JEE Main you can easily crack other exams. 

If you are preparing for JEE Main you should go through NCERT books and if you are preparing for MHT CET you should refer your state level textbooks. 

A lot of practice is required to crack both the exams so make sure you solve as many as MCQs and mock test series for your practice. 

All the Best!!