Victory road(for grass, ground, water, fighting, and ice types) and the water surfing path to the pokemon league(for electric types). All pokemon should be at least lvl. 55 with something to counter lvl. 62 Garchomp.
Victory road again. All pokemon lvl. 50 with a strong ice type.
Victory road and the sports places(which give alot of exp.). All lvl. 55 at least because of N's Reshram and Ghetisis's Hydregion.