The best Dragon Team would be the following pokemon:

Salamence-Fire Blast,Dragon Claw,Hyper Beam,Fly
Flygon-Giga Drain,Solarbeam,Earthquake,Dragonbreath
Altaria-Perish Song,Fly,Hyper Beam,Dragonbreath
Latios-Psychic,Recover,Luster Purge,Aerial Ace
Gyarados-Dragon Rage,Fire Blast,Hydro Pump,Ice Beam
Rayquaza-Outrage,Extremespeed,Fly,Hyper Beam

Just make sure to avoid ice and strong dragon moves, and your team will be pretty much invincible.