In general, just level up your pokemon more. Golem would be great for Nidoking and Excadrill. Just level it up and make sure it has Sturdy active every time you send it out; heal it up before sending it out, and Earthquake them to death. Walrein is vital, because of the field, both its STABS are special. It can dish out great damage; try using it against Claydol and maybe Garchomp, considering Garchomp's attack is monstrous. Lilligant kills Quagsire easily,. Hippowdon is bulky, but the rest of the mons can kill it.
Yanmega might not be the best, considering both Flying and Bug are both physic