My favorite dragon to date was a very old Red dragon named Stryx. One day before the campaign he was extorting towns and one didn't have anything to give him, so they gave him a pure maiden. Long story short they eventually hit it off, even had a kid. Then the fateful day happened where adventurers bust in to kill the evil red dragon, find out they can't because he's too powerful and kill his wife instead.
Stryx is furious, wants to kill every human on the planet for what they did, but he realizes it wasn't humanity's fault it was these damn adventurers that are running around in the land. So the red dragon now knowing there is good in people as well as bad creates a kingdom, and lets everyone know far and wide that a red dragon has a kingdom. Adventurers start flocking in by the cart full. He wagers to all, your hoard against my kingdom, winner take all. Invests all of his blood money back into the economy, his kingdom is the most well educated and well built. Also has one of the world's largest graveyards.