Like most Pokmon cards, the value of Moltres ex depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (FireRed & LeafGreen)
Dragonborn Champion is fine for helping you draw cards, but you need a way to reliably deal at least five damage to a player (probably with another dragon with flying)
This is, however, a very good time to praise Wizards and the designers of Unsanctioned on their decision to make these legendary creatures fit into a two color identity for the purpose of Commander
It goes something like this: Pay 2, activate Soulbright Flamekin targeting Agrus Kos
Some were originally pulled from booster packs, while rare Japanese promo versions were only awarded through the Pokmon Players Club