Anything that you need to buy (equipment-wise) for first year will not be necessary right away. You can take care of purchasing it during the first week (or maybe 2 weeks?) Sales reps will be at the bookstore with some pretty good deals.
With that in mind, this is what you need (going from memory):
Stethoscope
Dx kit (Ophthalamascope / Otoscope)
Blood Pressure Cuffs (Adult, Large Adult. Pedi is optional.)
Tuning forks
Reflex Hammer
Penlight
Pocket Snellen Eye Chart
Personally, I skimped on the BP cuffs, and went high-end on the stethoscope and Dx kit. In first year, you only use these to a marginal amount, but they ARE required for your standardized patient encounters.
As far as books are concerned, that's a matter of preference. To start off, though, you'll need a Netter atlas of human anatomy, which will become your best friend. I also highly recommend the Netter flash cards and the Rohen color atlas of anatomy ("Dead Body Book.") I would NOT buy the giant Principles of Osteopathic Medicine Book - you basically never use it.
I'd be happy to answer any specific questions on things you may need / not need.
-SB