That new retyping of Gardevoir to Psychic/Fairy is fantastic, now it is no longer Pursuit weak and is immune to Dragon-type attacks. Its Mega-Evolution is also excellent, so it is now much more powerful than Life Orb Gardevoir!
Gen VI ORAS
Gardevoir(F) @ Gardevoirite
Ability: Trace ---> Pixilate
EVs: 4HP / 252 SpA / 252Spe
Timid Nature (+Spd, -Atk)
Strategy is simple here. Come in on something that Gardevoir can force out, which is actually made easier by normal Gardevoir's fantastic Trace ability, like switching into a Vaporeon and tracing its Water Absorb, thus forcing it out as it cant do much. Set up with Calm Mind while going Mega as they switch, then proceed to sweep.
Shadow Ball + Focus Blast gives perfect neutral coverage, hitting pesky ghosts and steel types for super effective damage (Scizor is a thing but every Pokemon has their counters, no?). Hyper Voice is just insanely powerful, being boosted by STAB and given a 1.3x Boost due to Pixilate. It goes through Substitutes, it wrecks souls, just wow. Gardevoir had always been my favorite Pokemon, and it looks like I'm going to love her more than ever before.
As for people asking how does Gardevoir learn Hyper Voice, it learns it by move tutor at the Battle Resort in Pokemon Omega Ruby and Alpha Sapphire.