If answering questions is a habit for you, the NCERT book is sufficient. Be sure to read through each and every example. The quant portion would be more or less covered by that.
You can purchase a few competitive books by local authors for the logical reasoning, comprehension, and related section, which calls for time-bound critical thinking. As much as you can, speak English with your friends.
Keep in mind that the foundation must be solid. Try using your fundamental knowledge to step-by-step solve even the most challenging problems. Even if you think the practice questions are simple, don't skip any. Solve problems using paper and a computer. To learn time management, take practice tests.
To secure a seat at IIM Indore (IPM), you need to clear the IPMAT entrance exam. Now, preparation for this exam will be quite at par with most MBA entrance exams but it also depends on your academic background. For example- If you had PCM in your 10+2, you will find the mathematics part quite easy as compared to others. On the other hand, if you are fluent in English grammar and vocabulary, that part will go comparatively smoother.
My cousin cleared the IPMAT by self-study, and here is his insight.
Overall, self-study is sufficient for the preparation of IPMAT. Start with the basics like NCERT, and move on to high-level competitive books. Along with that do not forget some sample papers. Learn to manage time while solving the questions and you are good to go.