Noctrune is a high damage dps, he can be played as a jungler, he can solo lane and he's great at ganking with his teammates. This build is focusing on his autoattack and attack speed + some lifestealing.

Sense you start of with Boots of speed and some hp pots, you have pretty easy to gank in early level. He's damage is high in the first levels even without damage items. Use recall at level 4, try to not do it earlier. At your fisrt recall you buy a Vampiric scepter and as much as you can of The brutlalizer. Get you Berserker greaves as quick as you can, they improve you movement speed which is needed and you get attack speed. The Rest of the Build is Bloodthirster, Guardian Angel, Yomuu's Ghostblade and Infinity edge, high damage you stay alive a little longer and got some more armor penetration.

I use ghost cause if you chase someone and your not in range of using Duskbringer it's perfect.
Ignite is a good spell for almost everyone, it makes True Damage to the target which is around the 200 hp left, nice if you can't attack them and if your not in range. You can also use Smite but only if your gonna jungle. Flash is and option but not a recommended one. the rest of the summoner spells is not that usefull, Exhaust aint that good that you think, Nocturne don't need it. Clarity us useless, it maybe can help you the first 6-7 levels but after that you forget it and just kill the mana mob.

Nocturne is a good farmer, he makes a lot of damage quick, you can you Duskbringer to cast it at a minion pull run in and take it down in around 2-4 sec, effective and gives you alot of money

Nocturne is an excelent Jungler, but he haves som problems at the start, if you wanna jungle with Noc, start of with a cloth armor and 5 hp pots, recall as quickly as you can buy Vamiric Scepter and then take down the mana mob which is around level 3-4. He can take down dragon on his own around level 6-7.

Nocturne is an assasin, a great one, start ganking as soon as possible on Nocturne, at level 2 he can take down almost anyone in the game 1v1 which is great, and in late game he's ulti is perfect for joining teamfights or chasing down someone with around 1% - 50% health.