Initial playthrough of a new gen... Whatever Pokemon I like regardless of type. Only new Pokemon introduced in that gen.
I plan on having Chespin or Frokie as well as Pangoro and Malamar. Those are confirmed to be on my team. That means I will have either two Fighting Types or two Dark Types. Fairy Types will not be friendly to my team. So, hopefully I can pick up a cool Poison or Steel Type as well. But, I have no real rule for this playthrough except only new Pokemon.
My main game (X) will never be restarted. It will be my game for doing all the post game stuff, breeding, pokedex, etc. My secondary game (Y) will be restarted repeatedly.
My second playthrough and beyond... Special playthroughs. Generally MonoType. My first one will be to try out the new type...Fairy. And then I will go from there. I have a bunch of names to use (characters from my book) that match a specific type for the playthroughs.
Xerneas, The DNAntler Pokemon Currently Awaiting...SSBU, SSB3DS, Pokemon X, Pokemon Y and Watch Dogs.