Tips and what to unlock for 3BC

Just made it to 3BC the other day and today I almost made it to 4BC but I ran out of HP flasks before Hotk tbh i felt really Disappointed in having come so far in that run only to Fail at the last Obstacle so I was wondering what would be some good tips to help me be better and or some weapon/skill unlocks to get that would help me out in beating 3BC

P.s really hope I picked the right flair for this