>>17842914Firemoth went out of style for Gen VI. Sending one out will only get your ass kicked by Firebird so hard it won't be funny.
There are many ways to build a competitive team. However, bear in mind this gen's theme is bulk and priority. This means you'll face a lot of Rotoms, Talonflames, Aegislashes, Lucarios, etc etc etc.
Cloyster is pretty good as they describe it to you, but know it will NOT stand a single special attack. Want a powerful sweeper that's pretty bulky too? Mega Gengar. People stopped using it since Smogon (pic related) decided to ban it from their games because those retards couldn't find a guaranteed way to counter it, but just ignore them and play with the Pokémon of your choice.
