For getting confidence in electrostatics, i want to suggest have a rivision of 11th topics such as vectors,laws of motion,work,enery and gravitation at least. Maximum concepts are related to them. The electric force concept,electric field and electric potential concept are very much similar to gravitational force, field ans potential concepts. Electric dipole is somewhat different. Regarding electric flux chapter vectror dot product concept is needed and do all derivations first. Using Gauss theorem application is useful in finding electric charge or electric field. For capacitance first study capacitance of conductor,after that capacitance of capacitor will be easier. Making numericals on topics will give confidence. But if you have depth knowledge about vectors,newtons laws,work,energy and gravitation chapter of 11th topics, electrostatic will be easier.