This game is pretty challenging and tough - especially for RTS players who like to turtle, so you can feel less shame.
The design of the game specifically encourages rapid expansion. There is one resource, the population of the map, and it's a shared pool between you and the enemies. In this game, turtling does not work, because an enemy who expands to claim as many recruitment sites as possible will gain resources faster than you, and drain the pool faster than you can, so they'll have more to spend.
There are three dragons, each doing different damage and health. The one which does the most damage also has the lowest health. It's best used for quick surgical strikes. The one which has the most health does the least damage, and is intended to provide buffs and aura support for your troops. I've never really gotten the hang of the close-range support model, but I'm okay with the glass cannon version.
To help keep your Dragon alive longer, use the jetpack to dodge incoming projectiles. Some skills will let you use shields, increase your damage, heal yourself, go invisible, stuff like that.