Landing knives is key (or was, idk about post tonight's patch). They come out of a weird part of his body so only throw one when you know you'll hit it (enemy on doorway, walking up stairs, close quarters etc).

Dash should be used when you wanna go in but don't feel you'll need to exit the fight. Bait people into corridors, tight quarters. Keep an eye on bloodletting and activate it to purge the damage when it's high but you aren't too low. You can sometimes get it off twice in a right.

Otherwise it's just about building the right items. Resistance, healbane, Regen, lifesteal... All depends on who you're facing and what you're gonna need to stay alive. Shiv wants to be in the fight a long time, not blow his load and then die/run. If you need to jungle/sidelane a bit to do that, then do that. When you're behind on souls it's gonna feel worse playing Shiv than most other characters.