This is the build I tend to go with majority of the time. While many people like to jungle with Nocturne, I generally solo lane while someone else jungles. Nocturne is a great early game harasser once he hits level 3. He is amazing Mid and late game. However, he's not much of a carry champion but good enough to be able to wipe out 2-3 people on his own.

If I'm not farming or getting enough kills, I'll build my champ the way I have it listed. If I manage to get plenty of kills early game, I would recommend to rush a Bloodthirster first. Nocturne is a squishy champ so life steal helps a lot. From there I would build a Brutalizer for the extra damage, cool down and armor pent. Since he is squishy, I would go out and buy a Frozen Mallet for the damage, health and being able to slow a target. Late game, the opponents tanks start to get annoying so I would then build a Madred's Bloodrazor. Generally the game should be close to over at this time, if not and you have the money buy a black cleaver for additional damage and armor pent.

Also I get Ghost to be able to catch up to a player and clarity because he can burn plenty of mana and I love harassing lol

Everyone may not like this build, but I have been doing amazing with it. You will become nearly unstoppable late game, however you will be targeted first majority of the time. You can initiate first, but be prepared to die. But don't worry, you'll manage to get 1-2 kills out of it while your team cleans the rest up.