Five battles in a row, with no Pokémon Center in between, against teams from level 63 to 68: the Kalos League is the real test of your team. Here is, Pokémon by Pokémon, how to beat the Elite Four and become League Champion against Diantha and her Mega Gardevoir.
Aim for level 65 at least for all six of your Pokémon, and 68 for your best attacker. The Battle Chateau, the Lumiose City restaurants and the Horde Encounters on Victory Road are excellent training grounds.
In your Bag: at least fifteen Hyper Potions or Max Potions, about ten Revives, Full Heals and a few Ethers. The palace shop sells all of this, but once you go in, you cannot come back out.
