Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Well as you can see the primary focus of this build is for Jungling. Nocturne is one of the best junglers now in my opinion because of his passive being able to strike multiple enemies and even heal him. Nocturne can take down almost any enemy one on one when I use this build and is a great help in team fights being able to use his abilities to get enemies off of team mates.
The runes I chose were for obvious reasons because you want nocturne to be doing the most damage he possibly can at once. These improve you ability to penetrate tanks and hit crits on everyone. You can take down a squishy character in no time at all once you reach level 18.
Wrigglers lantern is an awesome item to have for this champion because it allows him to jungle easily and place a ward whenever necessary to avoid ganks and even possibly set up one. I chose the berserker greaves just because of the attack speed which is great for nocturne's passive. Guinsoo's blade is a perfect item because it increases your attack speed and ability power, even though nocturne isn't an ap character the small boost does help in some of his spells. The bloodthirster adds and amazing boost to his lifesteal and damage making him almost impossible to bring down and when you can finally buy the infinity edge it's pretty much over.
Creeping / Jungling
Pretty much the objective for nocturne is to jungle the entire game almost you don't really need to stay in a lane. Once you get some good items and have your ult the fun begins. Since nocturne blinds everyone he is the perfect jungle ganker. You can come up in a bush near a team mate and activate it and go in for the kill with out anyone else being able to react in time. Just make sure to ping who you are going to kill so your team mates can act accordingly.
There really isn't to much to know about Nocturne besides that he is an awesome champion and jungler. If you can farm early and often you can make this champion the most OP possible.