For the 14 team part, I'd say to draft RBs at least the first two rounds. I don't know your league settings or anything, but I'd imagine that if you wait until the third or fourth round, you'll be screwed at RB (which needs to be good).
For the dynasty part, draft young, but not too young. I see a lot of guys screw themselves for the first three or so years by drafting all rookies. Don't be afraid to draft veterans.