Get gardevoir is pretty simple, you just need rock smash, then you go to the underground railnet, in the walls there is some gray bricks you use rock smash in them, inside there are items, in one of them there is a item called corrupted pokeball, now you go to the pokeball shop in obsidia and talk to the guy who says he is a pokeball designer or something like that, after some talk and a blast powder he will give a ralts. And in my opinion you should replace noivern with gardevoir.