Nocturne Top is a complicated champion, in which he doesn't have a "perfect" mythic item for him. In a way, he is in a difficult spot for lane right now and isn't at his best right now.

Never build Duskblade, or any lethality top lane

It is recomended that you go the bruiser route or tank. Whichever one your team comp needs, its your choice really.

Building Goredrinker or Stridebreaker is ideal. Which one however, is a personal preference. It is completely optional to build either, so it is possible to go different routes like Trinity/Divine.

Nocturne can build many items in such, but not all work. For some games, going full lifesteal can be very usefull if they have no cc. There are different build paths that you can use for each team comp.

Axiom Arc is very situational

It is almost guarenteed every game you will start with Corupting pot

In most matchups, you are able to duel a 1v1 and win. Compared to Jax and Fiora, Nocturne can be very kill efficient in lane. Most of the time you want to fight prior to level 3 because that is when you are strong. In bronze you will likely be able to kill anyone at level 3.

Make Sure to time your spell sheild
It can be cc or a high damage ability and may take some limit testing.