I just use seismitoad, zebstrika, and mystic victreebel (because it has solar beam). My seismitoad's attacks are good against electric, fire, and rock. Also, I bought Overheat for Zebstrika, allowing it to battle against plant and ice as well as flying and water. I got past all the gym leaders, elites, and champions with those (and some others, which I'm too lasy to mention, like Unfezent.