I prepared for about 25 days for my exam and I passed. This is because I had taken my MRCP 1 just 4-5 months before my AMC1. In hindsight, it was a bold risk that I took and would NOT recommend anyone to take this test with such a short duration of prep.
Ideal prep time would be around 2-3 months if you have strong basics and 4-6 months if your basics are weak.
I personally used only 2 resources:
- AMC handbook for MCQs
- John Murtagh General Practice- selected topics, read local guidelines
Some other recommended books that I did NOT use are:
- Oxford Handbook of Clinical Medicine
- Anthropology of Medical Conditions
- Harrisons Principles of Internal Medicine
- Kaplan USMLE Step 2 CK
There are quite a few qbanks available online which you might use for your prep.