This is my build for nocturne the king of the jungle.

So first you want to get normal starting items a hunter's machete and 5 health pots. After that you can get either a sweeping lens or warding totem, i tend to go with the sweeping lens to clear out wards to catch the enemy off guard when you gank.

On the first back you should have enough for a spirit stone, boots of speed and a vision ward (or a doran's blade your choice). The vision ward will go in the bush infront of the enemy red buff where it curves, the one diagonal of the golems, most people never check that brush until late game by placing the ward there you can catch the enemy jungler taking red buff and help push a lane or do a buff steal

Nocturne is a great initiator, if you go full glass cannon you will die after diving the back line. With nocturne you don't need that much damage so it's best to get an elder lizard and trinity force. Trinity force works well with his kit the movement speed bonus is great for keeping on people to e them while they are on your dusk trail, the spell blade proc is great for trading. Elder lizard is good for finish people off the with burn and helps with clearing camps fast when there is a team fight going on.

In my opinion the best tank items for nocturne are sunfire cape and spirit visage. Spirit visage helps with mr and cdr which is really nice on nocturne but not needed. You could go banshee's veil however, he doesn't really need it since he has a 20 second spell shield for his w and it would just take up a space, unless the enemy team is heavy ap and you want both spirit visage and banshee's. You could also go randuin's however, I'm just not a big fan of that item.

Nocturne is a solid low elo (bronze,silver and gold) jungler his ult causes confusion in team fights which in low elo communication can cause a lot of problems in a match. Some do not expect a level 6 nocturne to dive under turret with his ult.

Farming with nocturne is extremely easy, his passive gives sustain so you should not die to camps unless you try to take one at like 30 health and below

Pros
Strong team fighter
Lots of damage
Great ult
Sustain

Cons
Ult can confuse own teammates
Easily locked down by cc
Squishy in the early game

Be sure to tell your team before you ult and make sure you are on the same page as them on who to focus if not then the ult is wasted.

pre 6 ganks are kind bad you just walk up q and e them that can be bad early one but after 6 do no hesitate to gank with your ult if you know you can get a kill or a turret out of it, or even a dragon. Normally i don't like taking risks and only gank if i know we can get something out of it so i normally just power farm so i can have items when i gank.

Nocturne is an extremely fun and strong jungler and is worth the time to learn if you want a new jungler that can go either glass cannon (not recommended) or tank with a bit of damage