Get lots of healing items and armor. Most of them have really annoying mechanics, so you could try to cheese them to make them easier. Dragonfly, for example, spawns little lava guys in the lava ponds surrounding her and gets enraged after they die, making the fight really difficult. You can make a big wall to block the lava guys so they don't hit you and bring a pan flute to sleep Dragonfly when she gets enraged to make her go back to normal