Listen to the others regarding the energy.
Focus on Water, Psychic and Electric (there will be water decks because Magmortar is so good) and perhaps Fighting. I am not even sure about fighting since you will see mostly Blissey with that weakness and that is a close-to-hopeless matchup anyway. A single energy of a type isn't enough to help you against those decks (I realize you can get than back in your deck with night maitenance, but it takes too long to get them out).
This way you don't have to sweat getting the right energy against G&G and Magmortar.