You can use, a dark type or water type or grass type. Do not use flying type as flying type because I am pretty sure claydol resists flying.
If you chose swampert use surf on it, if you chose sceptile use leaf blade on it.
Blaziken doesn't help at this gym. You can get a superrod in mossdeep and catch a Sharpedo off the island level 30+. Sharpedo is a dark/water type and just train it to level 40 and have it use moves like surf and crunch on it. Or You could go back and catch an absol. Train it to lvl 35ish and teach is shadow ball. You can get the tm for shadow ball inside mount pyre top floor. By the way you could also use solar beam on him, just weaken him a bit to yellow than solar beam.
Lemme know how it works out.
