Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
I've got a challenge for you. Defeat every gym leader using only the type of their gym. So only use Rock types against Roark, Grass types against Gardenia, etc. Then use 6 of those pokemon you used, all different types, against the elite four.