League of Legends (LoL) Question: what item will make nocturne a killer in early games, top lane not a jungle

Ravenous Hydra. Your Q already gives you strong damage. Hydra lets you sustain off every wave and clear it very quickly, making it really hard for your lane opponent to trade since you'll always have more minions. Double doran's blade and hydra would be good for early laning.

If I were to play Nocturne top or something I'd probably get Ravenous Hydra, and then Youmuu's Ghostblade, Statikk Shiv or Blade of the Ruined King. Not quite sure which one since I haven't tried each of them in lane. I've done hydra->ghostblade though and it seemed pretty strong. It's nearly impossible to escape a ghostblade nocturne and he pushes towers super fast. You can get Last Whisper third and that'll be all the damage you need for the whole game.

Another option would be Trinity Force. Expensive as hell but it's a great item on him. If you're going for a more tanky build you could try triforce. I wouldn't bother with it if you're going lots of damage because it doesn't scale well with other offensive items.

I played it like 5 games nocturn top.

Build order should be something like;
hydra+blade+merc boots than 3 defensive item for example : randuin,sunfire,spirit visage

Win lane and go lvl 6 mid or bot for some free kills because they dont expect a high dmg nocturn at their lane