How to prepare for GATE Instrumentation Engineering ?

Understand that you cannot get 100 marks in GATE 🙂 I think even 90 is a tough ask. Toppers answer around 85-90 marks (of course it depends on the paper’s difficulty, but the general trend is this).
NEVER OMIT ANY subject. I find most students omit a subject based on the weightage.
Self-study works, but I would suggest joining a coaching institute if you unable to understand concepts.
Aptitude & Maths will make a huge difference in your scores. Around 30 marks (including aptitude) is really easy to score. They are usually less difficult and direct than subject questions.
Solve as many previous year GATE problems as you can.
Learn concepts only from standard books
Use standard books.
Solve 10–15 Questions Daily.
Make Your Own Formula Sheet.