I have a friend who completed her BA in Political Science from CSJM. Here are some of the books she suggested. 

• Laxmikant - Indian Polity or Gauba
• J.C Lahiri, B.L Fadia - Public Administration
• World Constitution - Vidya Bhushan
• Political Thought - Asraf Ali
• U.R Ghai - International Relations

These books are necessary for B.A Political Science. 

Here are some other factors that can help you get a gold medal. 

• Conceptual clarity.
• Real-world examples should be provided to back up your answer.
• Finish the whole syllabus.
• Read simple language books. Avoid using guides.
• Every day is a challenge.

Having good handwriting also helps.