These are just ideas that i made up when i saw his kit.
This is just theoretical, i have yet to play yasuo. I just want people to try these builds and see if they're viable.

I was thinking people would argue that Triforce isn't too good on him because it gives mana, which Yasuo doesn't use. Realize though, that if you remove the value of the mana from the value of the triforce, the triforce is worth 3892, which is 189 gold more than it costs. Doubling the value of the crit chance makes it worth 4392, 100 more than it is worth on anyone else (that uses mana) Adding in the bonus AD it would give by using Atma's impaler, the total value of a triforce on yasuo would be 4527, which is extremely gold efficient, making it worth 824 more gold than the item costs.

This is also not taking the passives or the movespeed into account.

If one were to add the movespeed from the passive into account, the item would increase in value by 260 gold on hit, and 780 on unit kill. (not including the 8% boost in movespeed)

The movespeed of the item is worth 403 gold on Yasuo if he has tier two boots

The item, on hit, with the movespeed boost, is worth 5190 gold on Yasuo, if he has an Atma's impaler. (this isnt including the 8% boost to the bonus movespeed)

(Does not include passives like Spellblade or Guardian Angel, or any form of penetration.)

Offtank (Fragile) Yasuo:
20,707.74 gold value vs. 17,193 gold price = 3,514.74 more value than price.

Glass Cannon Yasuo (Current Meta Build):
15,446.1 gold value vs. 15,450 gold price = 3.9 less value than price (note, this doesn't include the value of the percent armour pen, because that varies.)

Assassin Yasuo:
20,178.8 gold value vs. 17,078 gold price = 3,100.8 more value than price

Offtank (Durable) Yasuo:
21,388.44 gold value vs. 16,408 gold price = 4,980.44 more value than price

Jungle Yasuo:
17,842.15 gold value vs. 15,450 gold price = 2,392.15 more value than price

Most cost effective: Durable Offtank
Least cost effective: Glass Cannon

Offtank (Fragile): 1243 DPS

Glass Cannon: 1387 DPS

Assassin: 1434 DPS
Assassin (with Youmuu's active): 1764 DPS

Offtank (Durable): 966 DPS

Jungle: 1464 DPS

Highest DPS: Assassin (with Youmuu's Active)
Lowest DPS: Offtank (Durable)