This is my idea for a Tibalt themed RDW:

4 Grim Lavamancer
4 Vexing Devil
4 Faithless Looting
4 Geistflame
4 Shrine of Burning Rage
4 Tibalt the Fiend Blooded
4 Chandra's Phoenix
4 Volt Charge
4 Slagstorm
4 Reforge the Soul
20 Mountain

The idea is that Tibalt provides fuel for Lavamancer, card advantage if he discard Chandra's Phoenix or a flashback card, and his -4 ability works lethally well with Reforge the Soul. Most of the other cards have considerable synergy, with Looting/Geistflame/Volt/Phoenix charging Shrine, Reforge playing off well against all the cheap spells, and Faithless Looting being a general all-star.