I use this Master Yi build when jungling, and almost every game I am able to go positive by quite a gap.

The magic penetration is useful for when you use your alpha strike to gank other champions, or simply for jungling. The crits and attack speed help as well.

Overcompensating in offense is what keeps this build strong, and by going 21/0/9 with the masteries you get a high damage output early game while still earning the much needed experience.

I start out with a cloth armor, 3 health pods, and a mana pod. This allows you to stay in the jungle longer than you would normally, and the mana pod gives you that one needed meditate or alpha strike.

I try to swiftly get madreds for the jungle, and then follow with the boots of speed. This makes it easier to jungle, while also moving faster for ganks. I turn the madreds into wrigglers, which gives me much needed lifesteal and wards for map awareness.
Trinity force is critical in this build. The phage gives you extra bulk, while slowing the opponent. The sheen allows for your attack after the alpha strike to hit hard, and the attack speed and movement speed is also nice.

After this you can branch out. I tend to go for phantoms dancer and starks fervor, for increased movement speed and the lifesteal. However, I've found that if you have a surplus of gold at this point you can take the hextech gunblade instead of starks, which still gives you lifesteal but also gets you AP, AD, and spell vamp.

To finish this build, i go for infinity edge for obvious reasons. Then i sell the wrigglers lantern for a bloodthirster, because at this point the bonus damage for minions is trivial.

I try to level up my Alpha strike first, then the wuju style. Level up your ult whenever you can and get the heal to two so its just high enough to save you from a tower blast.

I tend to take smite and heal, smite for the jungling and heal for the turret dives. However, exhaust, ignite, and flash could probably be useful.

I don't recommend taking clarity because you have wrigglers, and don't take revive either because you should be smart enough to stay alive.

PROS:
Good at ganking
Great at farming minions with alpha strike
Unstoppable mid to late game

CONS:
This build still leaves Yi pretty flimsy if he gets exhausted or stunned
He is pretty weak early game, especially if he keeps having to cover for lanes

I recommend starting with the mini golems. Alpha strike them and hope for a crit. If not, pop a health pot and start attacking one of them. If your health gets dangerously low, pop your heal, but save the smite until the first golem is dead. Alpha strike whenever you can.

From here, I go to wolves and then to banshees when I have smite again for the blue banshee. Depending on the opposing team, I can sneak into their jungle for wolves and banshees, too.

I tend to avoid golem until i have wrigglers or at least madreds. I avoid red until I have taken red and know that I'm too high level to fail. The same rule applies to dragon.

ALPHA STRKE

One thing that tends to aggravate people about this build is that it's very single player oriented. Yi can participate in team fights, but his beauty is in his ability to jump into the battle to dish out damage, and run away when he needs to. People tend to not complain when you have more than the entire team in kills, though.