+Spd -atk Leif skills?

-atk kind of hurts, but in most cases should be mitigated by the side effect of his weapon. (+7 if you're hitting high def targets) in any case, a fury/desperation/drive atk combo is budget.
if you really like him, you could do swift sparrow/desp/heavy blade seal/option of C (maybe threaten spd). As for special, luna would work. He's pretty fast.