which book I first referred for my jee starting preparation. I enter in 11th and I want to start my iit jee preparation

Hello student prefer NCERT to build your basic concept and make sure you do each and every example and exercise questions of Ncert before jumping to a reference book after completing ncert thoroughly refer to your coaching material or any reference book as mentioned below -
Concept of physics by HC VERMA
OP TONDON CHEMISTRY
JDLEE chemistry
Rd Sharma Mathematics
Arihant practice book for Jee main

You can also subscribe to careers360 knockout package for preparing and qualifying the entrance examination, it offer you 100 percent money back guarantee if you do not qualify - https://learn.careers360.com/knockout-jee-main-april/

Feel free to comment if you have any doubt
Good luck