you will give badges to me in exchange for a pokemon i will give you.type depends on the type of the pokemon the gym leader of your badge given has.the level also depends on the highest level of pokemon that gym leader has.
but,you can also collect badges for the Elite four.once you gave your badge for a pokemon,you need a new one if you want to compete on the elite four.
The rarest pokemon to be given is a: Shiny pokemon
but,the MOST rare SHINY pokemon in this rpg is:
SHINYLUCARIO!
it is also the second rarest to have a riolu.but we have gone out of our discussion on badges.check the rarity list on the help board.