Analysis of mock exams and correcting your wrong answers is critical.
If you have already started off with Quants preparation and you need higher difficulty level to crack, I suggest go with sarvesh Varma. If you're at just intermediate level, go with Arun Sharma, questions are clear concise and Lucid explanation is given for better understanding of fundamentals and Steps for approach. You can also refer books by nishit Sinha for Quants and Data Interpretation as there are quality numereical problems in this book.
For Verbal ability and Logical Reasoning, Just refer TIME Coaching Material.
Make sure you give ample of mock exams every month. All the Best.
But if you can get access to some preparatory materials then that would be great. Even their online mock tests are very good. The key is practicing and consistency. Subscribe to online websites and give mock tests regularly. Give as many as you can. Brush up your concepts regularly. Analyse your results and determine your weaknesses and strengths. Manage your time well. Be in touch with the news through apps like economic times and business insider.
There is a lot you can do if you stay focused and consistent.