Hii Siddhant 

Try to start with chemistry section because of the fact that  it takes comparatively less Time as compared to maths and physics. Around 45 min will eb sufficient.

Then go to physics followed by mathematics. Around 50 min will sufficient. For Maths you can dedicate around 1 hr rest of remaining time can be used for revising the question and solving the unattempted one's.

Tips:

At the max 2 minutes should be alotted to each question in Jeemain as 90 questions there with 180 minutes.

Dont focus too long on one problem if its difficult you can simply move ahead. 

You can also save time on easier questions and use renainder time for tougher questions at last as and when you have time.

Hope the answer is helpful. 

All the best