First, A quick note before I begin this section of my guide. (About this)

If your game gets to end game, I suggest trading the Youmuu's Ghostblade out for a Randuins, It gives you just that much more survivability. Also, I take Ghost (you'd be surprised how much this helps early game ganking) and Smite as summoner spells as this is a Tanky DPS Jungle Nocturne build. I recommend even mixing up skill order to gank early, As early level ganks with Nocturne are devastating. Any of the runes I suggested in the cheat sheet above are viable for this champion.

Alright, Let's start off with the path I use when Jungling Nocturne & A recovery path to use if your Blue is stolen by the enemy team, because I see FAR too many players that don't have or even attempt a recovery path if they're blue has been stolen.
Normal Jungle:
First, Start off at blue, Ask for a leash, the better the faster your jungle, the more ganks you can give out. the best leash is to just over half hp to the point where you can basically just smite the golem.
After getting blue, progress to Wolves, Focus the large brown wolf as it will cause the most damage. After slaying Wolves, move onto Wraiths, Again focus the blue one, the one with the most damage output, Then move on to Golems and finish these. If your using the runes listed you should have no problem with getting red buff as well, But if you aren't, You might end up getting really close, or not even being able to do it at all, if you feel you can't you should probably recall before doing that, and attempt to grab a vampiric scepter, or a longsword with some health pots.(depending on your preference). After you finish red, Look for an open gank & coordinate one with your teammates., or ask your teammates to let the enemies push their lanes, Nocturne is a very strong early game ganker, and can often help to leading his team to victory with the early ganks or turrets to you can get on your enemies.
Recovery Path:
You should use this if those jerks from the other team stole your blue!
I recommend starting at Golems or Wolves and then going off to Wraiths and finishing the other creep camp that you didn't start at, then either ask for a leash on red or go gank a lane or cover a friendly lane to help make up for the experience you lost from not having blue :(

Aside from Nocturne's jungling usefulness, He can also use his ultimate to help protect his team's carrys from the other team's carrys. You'd be surprised how well this works with a Caitlyn or Kog' Maw.

Pro's
Great Jungler
AOE passive with lifesteal
Amazing ganker, after 6 he's just amazing. (he can even bypass wards with his ultimate, even helping him to be even more of a sneaky beaver.)
Tanky DPS, After you get a frozen mallet, their's almost no way to escape Nocturne with an ult up, Frozen Mallet constantly slows them and your Q gives you, I believe 35% movement speed if you've hit them with it. You can use your ultimate to chase them after they flash, improving its usefulness. You basically have a 65% movement speed difference between you and your assaulted enemy.
Fear? 2 seconds? With your damage? *Beautiful*
A spell shield, That makes it so that you KILL FASTER if they use an ability on you when you have it, Makes them wonder if they should use the ability or save it for when the shield comes off.
Good in solo queue especially, and when using ultimate in team-fights amazing in 5v5 premades.

Con's
People get scared when they see a Nocturne ult and sometimes end up running into a bush, not allowing you to dash to them :(
Somewhat mana hungry
This build is more for supporting an AD carry, to deal nice damage and take it as well.
Not much else to say that I can think of right now, Nocturne's just a really solid tanky DPS champion.