Flash and ignite are obvious for an ad carry unless you want to get cleanse or exhaust if you'd like.

The idea of this item build is to make Yi have 100% crit strike chance rather than have lost of attack damage and no attack speed at all.

So here is how the math works for the crit chance and damage:

[Crit Damage increase]

[*] When ever a crit is landed it is multiplied by 2.

[*] The infinity edge increases that to 2.5

[*] And finally your lethality mastery gives you and extra 10% extra crit damage.

[*] also the runes give an extra .05 extra attack damage

[*] maxing it out at 2.65 crit strike damage bonus.

[*] You can replace some of the attack speed runes with crit strike chance bonus instead if u want the extra damage to troll the hell out of people.

[Total crit Damage}
your total crit damage would be from 285 to 755 points of damage. so basically you would be doing 755 points of damage every time you strike.
[*] if u include your attack speed which is maxed out already at 2.5 as that would be 1887 points of damage per second.

Pros

[*] Extremly high attack damage
[*]Very fast attack speed
[*] You can kill enemies ridiculously fast

Cons

[*] Very Squishy target
[*] Your screwed if u start getting focused in a team fight
[*] your ult is almost useless becasue your attack speed is already maxed out
[*] your ult is only used to catch up or run away from an enemy or to not be slowed.