See there are no hard and fast rule that with coaching you can crack JNU and without it you can't. So don't keep this in your mind and focus on the subjects.

Now for MA Economy you should prepare according to the syllabus and prefer the most efficient books from where you can clear your doubts and can strengthen your concepts. You should solve the previous year papers and give as a test so that the efficiency in a stipulated can be maintained and check it yourself. This will work as Mock tests which will ensure your accuracy in exam time as well as boost your confidence.

Some of the books that Might help:

• Microeconomic Theory by Hal Varian
• Intermediate Microeconomics,7e by Rubinfield and Pindyk
• Microeconomics Macroeconomic Theory by Dornbusch and Fisher
• Macroeconomics,6e by Mankiw
• Macroeconomics,6e Mathematics by RGD Allen
• Mathematical Analysis for Economics by AC Chiang
• Fundamental Methods of Mathematical Economics by Sydsaeter and Hammond
• Mathematics for Economic analysis Statistics by Nagar and Das

You can get the JNU previous year question papers from the official link below:

https://admissions.jnu.ac.in/searchquestionpaper.aspx

I hope this answer helps. All the very best for your future endeavors!