Dear Aspirant,

you can first start by studying from the NCERT Textbooks. NCERT textbooks are very useful for understanding the foundation of each of the topics. Once you go through all the theory part of the topics, you can move on to solving the questions in the textbook, this will help you understand the concepts even better. There are generally two kinds of questions in the NCERT textbooks, short and long type.

As you have completed class 11 then you have to move on with the knowledges of Mechanics you have gained and have to apply them in the concepts of Electrostatics. So you should have a good base of simple concepts like Vector and basic Force and Torque concepts which will really help in solving numericals of electrostatics.

Start with NCERT or any book that you prefer and go through it. Read the concepts thoroughly and don't waste a lot of time on only theories but also try on practicing problems from HCV or any other book you prefer.

I hope this might help. All the very best for your future endeavors!