Im planning to play pokemon x/y "competitive" just to see how much depth this game really have and also to get more fun out of it.

Are there common teambuilds? Is there some sort of "meta" in this game? Like pokemon that pretty much everyone uses because there are tierlists or something? I heard garchomp should be pretty op in this game, which is a shame since i really liked it even before i heard there is some sort of competitive gameplay in this game. And what are the basics of competitive playing in this game? I often hear leftovers are pretty much no brainers and i already heard and tried ev training and also know about ivs. what more should i know when im starting?