Here's my strategy!
Pokemon i used:
Tyranitar ( i used a Elemental Dragon one)
Any Water Pokemon (I used a Tentacruel)
Pichu (your starter)
Tentacruel (Any Water/Physical Move)
First use the Pichu to get in defense lowered for Tyranitar to beat it, use a water pokemon to beat claydol more, but Hydro Pump is a water move, and if your Tentacruel has Screech, use it to replace Pichu's Charm.