Impoving Noc

Pardon me, but what?

Are you asking "what would be a good way to improve Nocturne" and that damage would come from armour or attack speed (2 things Nocturne is know for?)

I prefer an attack speed build but it really depends on the team comp and the enemy's team comp etc

The primary reason you use Nocturne is the utility of his Ultimate and the ability to cut off and/or outnumber the enemy team. Build for the situation, not towards a given pattern.

That said, I like Devourer the most on him. Everything else is accessory if you think strategically enough.