Hi Ronak, thanks for your query.

It is nice that you are going to prepare from now for GATE exam. For preparation of exam, you should invest atleast 6 hours daily to brush up your concepts starting with the subjects which you'll study in second year like Digital Logic and then Theory of Automata. Engineering Mathematics which you must have already studied in first year and will study remaining in second year. 

After studying a concept, also practise previous year question paper so that you can understand the level of questions in exam and that will bring you confidence to solve questions. Attempt test series which are available online or in paper form. Test series are most important to test your skills and concept understanding.

Hope it helps!