How I should start prepare for gate

Start with watching the interviews of last year toopers, then you will get a brief idea about the books you should check. 
Use GATE tutor 2018 of ARIHANT, its great book, 
Solve previous year gate paper as much as you can,
Join online test series(at least 2) out of MADE EASY, GATEFOURAM, ACE, etc.
Plan a fixed schedule and follow it with discipilne,
Most of all have faith n yourself(the most important tool) always..
Best of luck.