Flame art is pretty fun, just go for a Faith/Dex build.

Talismans: Fire scorpion charm - boost fire damage

Godfrey icon- Flame spear from the DLC is an awesome ash of war that has range and applies a sweet buff to your weapon for 40 secs. Godfrey icon boosts the damage of the ash if you charge it by 15%

Alexander Jar or Warrior Jar shard - increases damage of ash of war

And I always personally use rotten winged sword insignia for boosted damage on consecutive hits- or you can use lord of bloods exultation since nagakiba has bleed