Gallade has an extra-ordinary attack stat and its speed stat is relatively impressive... so I suggest going all-out attack on the opponent with it... my preferable move-set would be :
1. Night slash (the gost type is done for)
2. Psycho cut
3. Leaf blade
4. Ice punch
if with this move set... gallade is given a "quick claw" or "Scope leance" to hold.. well that would be a nightmare for the opponent !!!
This set of attack would also allow it be an effective attacking option against Dragon, water, ground, rock etc types.