Score cannot be predicted as it varies depending upon various factors like number of students appearing for the exam, difficulty of paper set, etc. 

For getting admission in any IITs across India a candidate must first clear JEE Mains then only candidate can give JEE Advance. Admissions are done on basis of JEE Advance marks. 

For preparation read NCERT Textbooks of 11th and 12th standard of Physics, Chemistry and Mathematics. Practice Multiple Choice Questions of each chapter everyday. 

Give equal attention to every subject as they are all equally important.

After NCERT Textbooks read reference books. They are really helpful if you study them well. 

Don't waste time on unnecessary things. 

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