Self-study is the best tool to score well in examinations. Since JNU is the dream institute for most students, the competition level is very high, but you can crack it with strong determination and dedication. If you are good at the basics and theories that you studied at graduation, then half the job is done. Try to solve the previous year's question paper, which is available on the official website of JNU.
Some important topics are listed below
Strive hard and give your best.