Gardevoir eh? I think I have a few Gardevoir sets for you.
Gardevoir @Light Clay
Nature: Bold
EVs: 252 HP / 128 Def / 128 SpDef
Ability: Trace
-Thunder Wave
-Reflect
-Light Screen
-Destiny Bond
I've used this exact set for my suicide-lead Gallade when I was once a Psychic gym leader here, and it should work for Gardevoir too.
What this Gardevoir does is first T-wave the opponent to paralyze and become faster. After paralyzing the opponent, you have the option to set up screens or surprise the opponent with Destiny Bond. In an ideal situation, you would have the opponent paralyzed and have both screens set up and then use Destiny Bond when Gardevoir is close to fainting. This makes Gardevoir an excellent Pokémon to lead with and give support to the rest of your team.
Is there a particular kind of Gardevoir that you'd want? One that attacks, defends, etc.?