im doing the ifrit quest solo mode and he3s kicking my butrt what the best way to kill him oh im a smn/whm should i change my sub to blm

First you should make sure you have the supplies (drinks and potions). After that start the battle, run up close to him, cast carbuncle and then send carbby to attack him. Run as far away as you can and when Carbby dies, re-cast him. This time use your drink (either melon or yag) and then use your 2hr. Do shinning ruby (do NOT move). After Carrby does it, run as far away as you can away and once carbby die, re-cast him and do another shinning ruby. Stand until ruby is done then run as far away as possible. You will probably need to drink a new juice if you were using melon, if not then just wait for carbby to die again and re-cast him. Do 1 last shinning ruby and the fight should now be over. If it isnt, just run away again, re-cast carrby and keep repeating this.

Use potions whenever your HP is in yellow (or below 200, whichever you prefer). If you want, you can use ether to make the fight easier.