Red mana= Dragons
What about black and green?
There are 13 dragons with only black and green mana costs.
Skithiryx looks pretty cool at 4 power flying infect with
regeneration and 1 mana haste option.
Kokusho, the Evening Star is perfect for multiplayer. Lifedrain and gain.
Deathbringer regent can be a great 'oh crap, I'm way behind I gotta do something' creature.
There are a few more megamorphs that give +1/+1 counters to creatures or do things to opponents or give stuff to other dragins you control when the dragon dies.
Search on gatherer for dragon creature type, not blue not white for all the details.
Good luck on trying out Commander! There are a lot of players on this site that can give great advice on cards specific to what you are trying to do, and give a good explanation why. The site has helped me a lot and I hope it does for you as well.
Dragons are so cool