Logic dictates that, in a game like this, one stat will end up being more important than others. My bet's on attack power. Granted, I'll keep my speed up just enough to attack opponents first in the area that I'm in.
Also, as with any RPG, the beginning is easiest if you boost your offence, use it to skip through quickly, and, with a bit of luck, I'll have time to catch the other stats up while I'm ahead of the others.
Volke rawks. xD