blade of the ruined king and grez spectral lantern should be situational items, dont bother getting them every game.
and plus you should only get 1 life steal item, not so many, and bloodthirster doesnt exist on TT
also you'll need defensive stats especially in TT, theres only 3 targets for the enemy to choose from, chances are your gonna get attacked, and thus you'll need resistances to avoid being killed. you cant rely on just lifesteal because you must attack for lifesteal to be a defensive stat. the moment you get stunned, your dead.
with nocturne, hes pretty much all situational in terms of build.
so first you should have boots, berserk as a default is good, but if you find yourself against a team with tons of magic damage and snares and slows (not consistant but in combo) then merc treds will do you better
then you need some kind of damage item to help with farming, brutilizer (later turned into black cleaver) is a good choice, all the stats on it are very useful to you and the stacks are easily applied with nocturne.
now you'll need a defensive item, I wouldnt go with frozen mallet because you have a very easy time sticking to your opponents with your shadow and fear, instead I would go with a runduin's omen if your looking for health and against a lot of auto attackers. if your up against a caster focused team then banshee's veil could be a better choice. if its a well rounded team with all types of damage, and are mostly hybrid style champions, then bulwark will be a better choice.
now you'll want something with a high attack speed, something such as phantom dancer, statikk shiv (great if you have other crit items to make the shock do more damage), sword of divine, or zephyr (only if you went with berserker greaves) wit's end is also a good choice if you need that extra magic resistance.
now there you have your first 4 items. the next 2 will be determined based on how your doing, how the enemy reacts, and if your being the focus of the enemy.
so chances are enemy team will see you as a threat, make you top priority to be focused on, so if thats the case, you'll want to go a little more defensive, while at the same time still getting offensive stats too. such as for magic damage, you can get wit's end, Mercurial Scimitar (especially this if your against a lot of bust CC combo champions), or Maw of Malmortius (if your against nuke champions this is a good choice), if your against heavy physical damage champions, then consider atma's impaler (this will get you a good amount of ad especially with the amount of health you gained from your first defensive item), or sunfire cape.
if your opponents are not focusing you much and giving you free reign, then go for heavy offensive at this point and get things that would wreck their day. if you have trap users or ambushers, then lightbringer could give you the upper hand and ruin their plans.
for a life steal item sanguin blade will be your go to item, though if 2/3 of the enemy team members has built over 3k health, then blade of the ruined king will do you good. or if the enemy team has mostly melee champions and they tend to clump up in team fights, hydra is a great item to use. this item is also good if your allies have abilitiles to group up enemies, such as darius, or orianna.
if your opponents have tons of health regen, or self healing in the kits, such as volibear, dr mundo, or just heavy lifesteal. dont be afraid to get executioner's calling. this will cut their sustain almost by half, giving you an easier time with them.
so as you can see, nocturne is a very complex champion when it comes to an item build, pretty much his entire build is very situational and thus must be made on the fly after observing the enemy. the only item that I can say should be core in every game is black cleaver because every stat is perfect for nocturne and can be useful in every situation.