Dear aspirant,

It doesn't depend upon the quantity of studying, it's all about quality. Means smart studying is necessary. As from previous few years CBSE or ISC questions are basically based on your understanding. You need to study the basic concepts from textbook of all the topics and need to make a short note on those topics. This would help to study you advanced books. After completing this go for advanced studying, as you are aspiring of full marks advanced studying and HOTS questions should be practiced. You can solve question papers of several competitive exams like JEE, BITSAT etc. Study smartly, choose your own way to remember a whole topic, solve conceptual questions, solve previous year question papers.

All the best.