Now, if gyardos happen to strike first, he could use... ICE BEAM! And I don't recall Dragonite ever learning a rock type move. Actually, strike that, ancient power. But still, Dragonite is terribly weak against ice beam. Because he's also a flying type.
for dem steel types, just have the dragonite with the hidden ability, and have it hold a weakness policy, after getting hit with a super effective move it will double the attack, after that just iron head the f*** out of them