Is it a wise decision to go for upsc civil services preparation without getting a secured job during graduation period

It depends on your confidence levels.If you feel that you will get through Civils, it is not at all risky thinking of Civils alone.It also depends on your financial backing and if you are sound that way , think of UPSC and there is nothing bad

Most candidates targeting UPSC exams keep themselves away from job in order to focus on the said exam. It is a tough exam and very difficult to clear if you are also in a job. In that case you cannot focus on it unless you are highly talented and have great grasping power. So do not worry, if you do