Dear aspirant

For preparing for GATE you can  to the best study materials like previous year’s question/sample papers, recommended books which carry most commonly asked topics, attempt mock tests once released by the authorities and topic-wise notes.

For previous year question papers and list of books to refer use this link:

What are the best GATE Preparation Materials? (careers360.com)

And answer to the second part of the question. If you want to learn coding you should probably start by learning C language. It is the basic language and will teach you simple and useful commands. Then you can proceed to other languages like Python, JAVA etc.

All the best