Hii aspirants

let me clear your doubt.

In first year all the branches study the same thing there is no branch paper. From 2nd year all the branches have to study different subject related to their course. Also in gate exam the question come from 2nd year onwards. So you can start your preparation from 2nd year. At first see the syllabus of gate exam of your stream and then study those topics in detail. And i will suggest you you to solve previous 10 year paper of every topic as you complete each topic.

so start your preparation from 2nd year or 3rd year.

I hope my answer Will help you out

Good luck