As you are in 2nd year so I would say better to focus on your B.Tech syllabus first because when you go for Gate, this syllabus would be helping you. So this is the time when you should clear all your basic concepts. And ideally, students start their preparation in 3rd year so I would also suggest you to do the same. And in 3rd year you can start your Gate preparation parallel with your graduation. And to get admission in IIT you have to first focus on your B.Tech properly and then your Gate score because both are very important to secure seat in IIT as it doesn't depend on any particular subject.

Hope this helps!!!

Good Luck!!!