Gallade works best as a Scarfer
I use:
Gallade (M) @ Choice Scarf
Trait: Steadfast
EVs: 96 HP / 252 Atk / 160 Spd
Adamant Nature (+Atk, -SAtk)
- Close Combat
- Night Slash
- Earthquake
- Ice Punch
Moveset hits everything Neutral as well as 13 types for Super Effective Damage. It hits main 4x weaknesses except Fire, you could use Fire Punch in a slot if you like, for Ferrothorn and Scizor, but using a fire type might be a better plan. This thing combos well with a Spec Heatran. EV's allow for full offensive support, giving over 350 Speed with Scarf, and 383 Attack. The HP EVs are for Seismic Toss and Night Shade, they take 4 hits to kill with 301 HP. 252/252 Attack and Speed are also viable.
Expert Belt is also a viable choice for this set, given the 13 type coverage.
Another set could be:
Gallade (M) @ Leftovers/ Life Orb
Trait: Steadfast
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Drain Punch
- Psycho Cut
- Night Slash
- Bulk Up
This is a bulky variant that allows for a open move pool. I like Gallade for Bulk Up, it has a high SpDef, allowing for it to beef up both defenses and pumps his Attack. The Moveset hits everything neutral or SE, not quite as good coverage as the former, but still formidable. Drain Punch helps with recovery. Leftovers is for recovery, use Life Orb if you are more offensively inclined.
The only thing I don't like about Gallade is his Speed, I would suggest a Speed pass, most likely Ninjask.
I hope this helps.