What grit(s) is most important when buying a whetstone?

When considering a whetstone, we always suggest getting a good quality medium grit / sharpening whetstone, which falls in the 600-2K grit range. If you buy one stone to begin with, start with an #1000 grit stone, which is the stone that is fine enough to give your edge good sharpness while still coarse enough for most dull edges. You will also have the most selections of stones when shopping in this grit rating.