Dear Dhrupad, ideally it depends on the position that you are being hired for. As usually GATE PSU is for entry level positions, they dont expect a mandatory work experience. If you have experience, it is good. But it is not mandatory to have work experience. But if you have had experience, you need to produce a relieving letter which will be subject to background check. If you think you need sole concentration to crack the job, you can absolutely focus on preparing rather than joining a company.