Nocturne is a very strong jungle right now with his strong clear, strong ganks post-level 6, and pre-6 he is still strong. The amount of attack speed he can get from his items, W passive and Lethal Tempo make him very capeable of wiping out any squishy target once his build comes online.

Lethal Tempo makes Nocturne hit really fast, and I mean really fast with items like BORK and Stormrazor. The rest of the Precision Runes allow him to hit faster, heal from kills, and take out the squishes with ease. Sudden Impact and Ultimate Hunter both work off of Noc's ult, kills make the ult come up more, and Sudden Impact makes him able to hit harder.

Items that give Noc huge amounts of Attack Speed: Blade of the Ruined King, Stormrazor, Bloodrazor. Plus the lifesteal on BORK helps Noc stay alive in 1v1s later game. The Crit from Stormrazor lets Noc start a fight by just bursting down a good chunk of health usually right off the bat. Duskblade is just more damage plus pen to deal with any protections an enemy might have and be able to do damage to a physical tank. Dead Man's Plate and Mercury's Treads just give Noc that little but of health and protections to be able to take that one hit that would otherwise kill him.

Start with your W just to get that 20% attack speed to start. It leaves you more vulnerable if you get invaded, and isn't good if you want to invade, if this was the case you could always just start Q and then get W at lvl 2. Nonetheless, start by maxing your Q for the damage when ganking pre-level 6 and post, then max your W for more passive attack speed. Your E is good to push an opponent off you if you don't want to or can't fight, or Fear them into your teammate when ganking to set up for an easy kill.