There's a quite alot of jungling guides both here on mobafire and on youtube.
Ive tried them and had difficulty doing them or even not able at all.

I made this guide for players who want to jungle and are low summoner lvl.

For the marks I choose atleast 2 armor and rest ARP.
For the seals just MP5 and glyphs just CDR.

You maybe change them but I have this setup shared with Amumu.

The masteries aint the best for mid/late game but neccesary for the early jungle.
Ive tried quite some diffrent builds but this works best and safest.

The first 4 items are neccesary to even be able to jungle in early game. The lantern can be changed but i like it since it gives free ward and helps with jungling becouse of the 500dmg proc.

After you got the items listed its all up to how you like to play him. Atmas and Infinity edge works well with him.

Why atmas? its true Nocturne aint got alot of health but his attack speed is crazy.
Lets say you got 2000Hp thats 40 extra dmg per attack, your'e attack speed is about 1,6-1,7 atleast.

Pack 1: Wrath camp - Smite the big one, cast Duskbringer and then attack the smalls.

Pack 2: Wolf camp - Start with Duskbringer and kill the big one first, wait 2 hits when Duskbringer is ready so you get the dmg buff for the next Umbra blades.

Pack 3: 2 Golems - Wait for smite to be ready or 3-4sec left before engaging. Start with Duskbringer and auto attack the right one then after Umbra blade proc go back to the left one smite him.

Recall - Buy Cloth armor and 2 pots

Pack 4: Big blue golem - Wait for smite then start with Duskbringer and use smite, pot as soon as you take dmg.

Pack 5-6: Wolfs and wraith

Pack 7: Here you can go 2 ways. Kill red but this is dangerous or just kill the 2 golems.

Recall Buy Lantern/Razors

Pack 8-9: Wolf Warth - Kill them then go Red if you didnt kill him.