If you are playing this build, you are going to want to choose either the Prophet or the Confessor class. The Prophet does start the game with a little more Arcane than the Confessor, which comes in quite handy when using Dragon abilities at the beginning of the game.
How To Acquire Dragon Fire Spell
When starting out, you will get the Seal as well the Catch Flame spell (if you are a Prophet). You’ll need to acquire it if you are a Confessor. You’ll also want the Dragonfire spell. To get this, you’ll need to take down Agheel the Flying Dragon.
In this build, you really won’t have much use for melee weapons. Instead, focus on getting your seal to +3, and the best way to get that is against the trolls up on the top of the hill. Smash that stone object and then head into the tunnels where you can pick up a bunch of stones.
Tunnel Boss
If you take down the boss in the tunnel, you’ll get the roar medallion. This will increase the effectiveness of “breath attacks” which Dragon Fire is (of course).
Dragon Communion Seal
Replacing the Seal with the Dragon Communion Seal is also a decent option.
If you’ve been looking for a good starting Dragon Priest build that uses pyro and Dragon fire to decimates enemies and bosses in a flash, then you might want to check this build out.