Tried him as full dps and didnt like his survivability late game after ulting on the enemy squishies, so i decided to make Nocturne a bit tanky. Please dont rate until you've tried out this build, please and thank you.

First guide so let me know if you have any tips.

MR blues, this will give you decent MR combined with merc treads early game. (thanks to Skorakk for idea). can be switched out for AS runes.

mana per lvl yellows, helps your mana pool stay fresh throughout the game. could switch out for armor or AS

Armor pen reds, self explanatory.

Flat health Quints, I like this early game, but can be switched out for attack speed or armor pen.

Pros
-great ganker
-viable jungler
-tanky with scary damage.
-speedy
-pusher
-useful team fighter
-fast defender against back dooring
-decent early game tower diving if done right

Cons
-damage output not to his full potential
-the fear time isnt very long till late game.
-decently high cooldowns

-Start out with cloth armor and 5 health pots as usual for a lot of junglers.
-Start at blue and keep going in a line, except skip red and go to golems.(should have got everything except lizard). After Golems, go back and get boots+pots, by the time you get back wolves should be back up, you should either get red or wolves first depending on which side you wanna gank; start with the one furthest away so that when you get the other one you can start doing some ganking on that lane.(remember to use health pots while running to lane so you have good health). From here on out it is your decision on ganking and jungling.
-Now you wanna turn your cloth armor into heart of gold and start stacking gold, you will now have some health for some ganking, and can maybe do a little tower diving with some help from your team and your ulty.
-next get phage for slows and damage, then finish out boots into merc treads, this lets you gank quite nicely.
-after boots finish phage into frozen mallet, after you ulty you will do decent damage, but at the same time your team can auto attack or ability spam all they want.
-next finish out heart of gold into Omen., now you are pretty tanky with armor, health, a little MR from Merc treads+runes, and you can slow, as well as doing a little damage. Also you will have some extra speed from omen added on to your already amazing speed.(plus omens passive and active =])
-next you finally wanna do some REAL damage, get black cleaver, this gives you the attack speed you need at this point in the game, gives you lots of AD, and of course reducing their armor is always amazing.
-after this core build there is other viable options, (which can be bought sooner than now). If the nukers are blowing their abilities on you, you can get another MR item and get either Force of Nature or Banshees Veil. If you feel you are okay with not having so much MR and the APcarrys are not fed, go for a Bloodthirster, this increase your damage output by a lot and make you somewhat more tanky by giving you lifesteal, and will also let you push late game by just life stealing through harassment by ranged carries. Instead of getting bloodthirster you can also get Infity Edge, although since we are not getting any other crit chance items I don't like this one as much. Stark's Fervor is also viable if nobody else is grabbing it. You can get ghostblade over Frozen Mallet but i seem to work better with mallet, its just preference.

After jungling phase is over, you can Q all of the minions as they are marching in a line towards you, then when they group up just auto attack and his aoe slice from his passive will kill everything. This will be very good for attacking towers and backdooring.

You will be tanky enough so that they will be focusing your carries instead of you. If they focus you then they should all die for it. For late game battles, make sure to save your ult for catching enemies running away mid battle instead of blowing it first thing.(usually, unless your team has really good positioning) Also make sure to time your Shroud of Darkness, don't just spam it hoping someone will hit you. Early game if you ult in, you can tower dive pretty successfully. Use your ult, use unspeakable darkness RIGHT AWAY, then use q+w (make sure Q hits) then auto attack until fear is implemented, then run away (maybe ghost if needed) and let your team finish them off considering you are only tower diving because your teammates has good health.

In order, max out R, Q, W, E

-Duskbringer: (Q) Nocturne throws a shadow blade which deals damage, leaves a Dusk Trail, and causes champions to leave a Dusk Trail. While on the trail, Nocturne ignores unit collision and has increased Movement Speed and Attack Damage.
Make sure you are constantly hitting your enemy with this before auto attacking, dont miss!

-Shroud of Darkness: (W) Nocturne empowers his blades, passively gaining attack speed. Activating Shroud of Darkness allows Nocturne to fade into the shadows, creating a magical barrier which blocks a single enemy spell and doubles his passive attack speed if successful.
use wisely, dont just randomly hit this button, wait till you see them cast a spell. Doing so will save your life.

-Unspeakable Horror: (E) Nocturne plants a nightmare into his target's mind, dealing damage each second and fearing the target if they do not get out of range by the end of the duration.
Great for ganking, make sure to stay close so they dont flash out of it.

-Paranoia (Ult): (R) Nocturne reduces the sight radius of all enemy champions and removes their ally vision in the process. He can then launch himself at a nearby enemy champion.
main ganking ability, coming out of nowhere! this makes you a scary jungler!

-Umbra Blades (Passive): Every 10 seconds, Nocturne's next attack strikes surrounding enemies for physical damage and heals himself for each target hit. Nocturne's physical attacks reduce this cooldown by 1 second.
This makes him a fast and viable jungler. Great for farming and pushing lanes.