I am pursuing Diploma in civil engineering. Should I continue my studies further or start looking for a job?

It's always better if you do a Masters degree. Because this is the age of competition. So, you're always good with a strong robust degree.

The decision entirely depends on you, but I will recommend, you should opt for a job (even if you start as an intern) and pursue B.Tech through correspondence. By doing this you will have around 3-4 years of market experience and a B.Tech degree at the same time.