Well i neither have the time nor have i played Nocturne enough yet to write an in-depth guide, but i still want to share my first experiences.
I play him usually as a jungler. Didnt test sololane yet but i think he would do great there.

Pretty standart for ad. Tested him with my xin zhao runes (see above) and they work well for me. For Quints you take what you like. I feel that Phage / Frozen Mallet and Banshee's Veil give enough survivabillity but do as you please.

Didnt test others yet. Those work for me tho.

Could not play further than the above yet. Still my thought of the endbuild would be like:
Wriggle's Lantern, Berserker's Greaves, Phantom Dancer, Frozen Mallet, Infinity Edge, Banshee's Veil

Notes:
-this is not the build sequence
-this is just my first experience
-some thoughts worth testing: Bloodthirster, Youmuu's Ghostblade, Black Cleaver, Mercury's Treads, Trinity Force
- i think most of the items are - again - preference

Again a routh overview:
-I start at the double golems: work them down with Duskbringer and autoattacks
--so far i think that Duskbringer works better than Shroud of Darkness. Also save smite for the Blue Wraith. I lose less hp that way
- Smite blue Wraith, Duskbringer, aa
- Wolves: same here
- Now I either take the two small golems from the ancient one, recall, buy boots/pots and get the blue. Or if mid lane /lane close to the golems is pushed by the enemy i go gank there and recall then.

Ganks:
- ping, ghost if needed
- learning by doing
- Duskbringer, Unspeakable Horror, Shroud of Darkness(to counter slows, stun, cc) and aa them to death

Ult:
-awesome for chasing and finishing off/later ganks
-keep in mind that you need vision of your victim


Teamfights:
-you are a assassin
-> do not initiate (thats = suicide)
-> pick out their carries, mages that usually stand in the back...i guess using ult to get their is perfectly fine (since you probably will not need it for chasing anyway since you are either dead or they only have tanks/hp monsters left after a teamfight)

- great jungler, not the fastest tho
- evil ganker
- fun to play, annoys enemies<3


-gimme your thoughts and ideas - i might test and include them
-again: this is a mere rough overview at the moment - not a in-depth guide