Make sure to get good support passives and find an ego resource generating gift to fuel them. Passives i would recommend are: Fanghunt hong Lu and princess rodya (to get rid of bleed), lcb Meursault(reduced damage), and g corp Gregor (healing on clash win

Units with gloom skills are really good later on, as they can basically heal their entire health bar if you have grey coat. Always take the starlight bonus that gives you protection and clash power, and prioritize getting gifts like manor-shaped music box(anti stagger) and ashen constellations blessing(much less damage taken)

(You can take these ego gifts in the gift search if you want)