I'm not sure if you're asking about these two Pokemon separately or as a duo?
As a pair, they both have a x2 Ghost weakness, very low defence stat and Gallade is still x1 against Bug and Dark moves. I wouldn't suggest using them as a pair, since they don't synergise well.
Individually, I would give them the following movesets:
Gallade @ Life Orb
Ability: Steadfast
EVs: 200 HP, 252 Atk, 56 Def
Nature: Brave
- Night Slash
- Drain Punch
- Ice Punch/ Psycho Cut/ Stone Edge (coverage move of your choice)
- Swords Dance
You can choose Bulk Up > Swords Dance, depending on if you wanted some extra defence boost as well. Stone Edge will deal with Flying types, but also Bug types like Volcarona, and also have the benefit of being non-contact, so Flame Body won't activate. Low accuracy though, so Ice Punch would be the better option against flying types.
Night Slash is the only option for your already existing Gallade; Shadow Sneak is my preference because of the +1 priority, but bulky Gallade can take a few hits.
Gardevoir @ Choice Specs/ Scarf
Ability: Trace
EVs: 252 Sp. Atk, 252 Speed
Nature: Modest
- Psychic
- Shadow Ball
- Focus Blast
- Trick/ Thunderbolt
I'd recommend the choice offensive set for Gardevoir. Psychic for STAB, Shadowball & Focus Blast for coverage, and either Trick to mess up an opponent's set & free up Gardevoir's moveset, or Thunderbolt for more coverage.
Life Orb is not fantastic for Gardevoir since it cannot learn a reliable recovery move. Gallade has Drain Punch, so Life Orb is more viable.
Taking synergy into account, I would recommend Scarfty as a partner for Gardevoir. Bug is x1 for Scrafty, Dark is x1/4 and Ghost is x1/2, and its Fighting weakness is covered by Gardevoir. It's a UU Pokemon though, and Gardevoir is really only good in RU. Spiritomb is another option to cover Gardevoir's weaknesses, but I rarely use it, so I can't give too much advice on that.
As for Gallade... there's not really anything that covers its Ghost & Flying weaknesses (except Helioptile...). I would recommend Motor Drive Electrivire, since it's a decently fast RU Pokemon, covers Gallade's flying weakness, and Gallade has Shadow Sneak to cover its Ghost weakness.
