Every chapter is equally important. 

Important chapters are dependent on other chapters. For example a student cannot solve sums of Kirchhoff's Law if he/she doesn't study basic things about current, potential difference, etc. 

I suggest you to complete the chapters that you start with then solve Multiple Choice Questions based on that chapter which helps to build concepts stronger. Solve questions in large numbers such that if a question comes from that particular chapter you can solve it. 

Prepare timetable and follow it. Make handwritten notes of formulas which can be revised before exam. 

If you still have any queries feel free to ask in the comment section down below.