Dear Time Gap:
We get a lot of inquiries like yours, not necessarily for the IAS exam but for all sorts of exams, such as the GATE (Graduate Aptitude Test in Engineering), GRE (Graduate Record Exam), GMAT (Graduate Management Aptitude Test), TOEFL (Test of English as a Foreign Language), and so on.
Consider an athlete who is planning to prepare for a competition. She needs to reach the competition from her current level of conditioning. The gap she needs to overcome for competition = (the target level of conditioning to be in the competition form) - (current level of conditioning). Effectively, she needs to fill the gap to be ready for the competition. At least two variables control the duration of time she will need to fill the gap: her intrinsic abilities for the sport and the practice routine. Given this, is there a universal answer for all athletes for how much time each will take to get to competitive form? Of course not. The answer at best can be that it depends on the athlete's current conditioning and the ability to progress towards a desired competitive form.
Your situation is no different. The amount of time you will need to prepare for any exam depends on your:
- Current level of competence for the test (current level of conditioning) and thus the gap from target level of competence (competitve form)
- Intrinsic abilities to learn the what is required: whether you are a quick learner or not, for the test content
- Practice routine: Method of practice and amount of effort on an on-going basis
We hope you can see the complexity of your question. There are too many variables for us to respond in a meaningful way to your particular situation.
For the practice materials, you can find relevant books in a local bookstore or library. The Web also offers preparation materials for free or for fee. Coaching classes are available as well. Which routine will work best for you also depends of your own constitution.
We do not recommend any products or services, as a matter of policy and practice. You will be well advised to seek recommendations from those who have been successful in the past.