On seven island, in the battle tower the strongest pokemon in your party has the same LV. as all the other pokemon in the tower. Use Gameshark or Action Replay to get like 999 rare candies or whatever. Go to your P.C, then take out pokemon around L.V 10. Go into the tower,up the stairs and win the battle. Then keep giving your pokemon rare candies until they're
around L.V 50. Then just take all the other trainers down but don't go down to heal or all the other pokemon will be around L.V 50!