I used sunlight spear and lightning stake. Lightning Infused Lothric straight sword. I used 6 HP and 6 FP flask setup had 1 fp flask left... I used an Ember during the fight to heal. Carefully time your spears, and weave in some melee if he gets in yo grill. His attacks are pretty easy to roll. When he flies into the air, run straight towards him and continue to the left, this should get you out of the fire in time, otherwise, you can roll at the last second to guarantee you dont get hit by the fire. Lightning arrow is good, but spear deals about 200 more damage, and can deal 1500 damage if you hit his head while in melee range, ~900 if you hit in melee range anywhere. When he's in phase two, wait for the laser beam attack, so long as you're just a little bit in front of him you should be able to get 3 lightning stakes off when he's exhausted. Being a little bit infront of him and just to the left or right of his head should avoid all of the laser beam attack. After you land the stakes, one more spear to the face will exhaust him and open him up to a final critical. Damage will depend on your build. This is not an easy strat, but it's incredibly fun, really encourages you to learn all of his hitboxes subsequently making him easier on each attempt. It's also INCREDIBLY fun to smash his face with lightning stakes. It just feels so right.