Viscous damage builds?

[Mending Mithrix Main]

I've been playing him as a healer and giving people extra lives but not being able to take care of myself in 1v1s is horrible.
Does anyone know what items to buy for bullet or spirit builds?
Because to me his spirit damage seems lackluster but bullet builds can do ok.

[Null Winter]

All-in on his bouncing projectile. It deals full procs on every bounce, so in a narrow space you can nail someone 3 times instantly with its base damage plus any "on Spirit damage" effects that don't have a cooldown/immunity period. Once they're nice and slowed by 3 huge puddles, if they somehow survived that insane burst, then you can use ult and just bounce back and forth between the walls to keep them stunlocked until death.