hi,

see preference is not less for chemistry in jee main. the questions structure is as follows:

mathematics- 25 question ( 20 MCQs and 10 numerical ques out of which 5 is must)

physics- 25 question ( 20 MCQs and 10 numerical ques out of which 5 is must)

chemistry- 25 question. ( 20 MCQs and 10 numerical ques out of which 5 is must)

so there is equal weightage is given for math, physics chemistry. while you are preparing for jee main you should give the same priority to each subject. however for tie breaking rule maths number is considered first, then comes physics and lastly chemistry. you may use btech companion guide by careers360 which would help you to do self study :

https://www.careers360.com/btech-companion