Dragon Types
I don't like to say this but Dragon Types just need time and effort to raise so we'll just list one. Dragon Types are useful because Fire, Water and Electric Type Attack are not effective. Dragon Types are strong and have good attack stats. Dragon Types are only vulnerable to Ice and Dragon Types so don't switch one in to battle a water type!
Flygon is a strong Ground and Dragon type. As with most Dragon types it has a 4x weakness against ice types and will probably faint with any Ice Beam. The upside of Flygon is that it is a Ground Type so unlike most strong Dragon types, rock types are uneffective. Earthquake is essential for this mystical dragon. Also Sandstorm doesn't work on this dragon and it has Levitate. The only downside is that it evolve from Trapinch which is very slow. You can find Trapich in the Desert of Pokemon Ruby/Sapphire/Emerald.
(Submitted by Manjyome (THUNDER!))Salamance is a Dragon and Flying type. It can learn Earthquake and Aerial Ace. It also has the Intimidate ability which is great when you battle Flygon and other Pokemon. It can also learn Dragon Dance and can make your Salamance very fast and strong. But! Like Jun, you have to become the strongest from small steps. It's the case of Salamance. Salamance evolves from Bagon and can be found in Meteor Falls after you climb the waterfall.