NCERT books are a good source for starting the preparation, but only studying from those books is not enough
NCERTs are a good starting point, but it will not cover the entire syllabus. You need to refer other textbooks, read general knowledge books and keep yourself updated with the Current Affairs. Apart from these, you should keep on gauging your level of preparation in regular intervals. One of the ways to do so is taking the Online Prelims Test Series from iLearn IAS. This test helps to identify one’s strength and weakness. So, accordingly one can prepare those topics in which they are weak thus making you more confident at the day of exam. I would suggest you to give this test series a try. You will definitely find it very helpful.