Welcome to my little jungling Yi build.

I mainly made this build as a reminder to myself, of how I play Master Yi. But I might aswell share this with you, as it some might want to try it out.

It is a jungle but also a gank build, you will want to level in the jungle and pop out every time you see a chance for a kill.

I use:
9 Marks of Desolation (Armor Penetration)
9 Seals of Evasion
9 Glyphs of Focus (Cooldown Reduction)
3 Quintessence of Desolation (Armor Penetration)

The Desolation marks and quintessences are a must for AD Yi, it burns straight through their armor.
The Evasion seals can be switched out with flat armor seals, but I see the dodge as being better since the armor can be dealt with by using armor penetration.
The glyphs of focus I use since you want to be able to use Alpha Strike and Wuju Style very often against your enemies, and if you don't take down an enemy hero while affected by highlander, you will be waiting for your cooldowns to be over a lot.

The 21/0/9 Build can be alternated a bit, but I like it as it touches some of the useful masteries for jungling, but will help later on when fighting heroes.

One way you can change it is take 2 points from Sorcery and put into Offensive Mastery to deal with the creeps in the jungle.

You can also change it into a 21/9/0 build, putting 3 in Hardiness, 1 in Resistance, 4 in Evasion and 1 in Nimbleness. This will give you some more survivability in the jungle as well. Yet this will cause you to lose improved haste, experience and increased time on neutral buffs.

Further explanation on buy sequence at the beginning is under Jungling.

I go with Wriggle's Larntern the most, it has a nice use against players like Evelyn, and is useful against Vayne when she uses her ulti-tumble combo. You can also buy Madred's Bloodrazor instead, but only if you end up against meaty heroes since it tears through their health, but you will lose the nice lifesteal Wriggle's Lantern has.

Berserker's Greaves needs no explanation, it has increased attack speed, which Yi loves.

Stark's Fervor is a lovely item, not only does it increase your attack speed and lifesteal, but also your teammate's attack speed and lifesteal.

Youmuu's Ghostblade is a questionable item, but I use it since it's a mini-Highlander, it also has cooldown reduction, which is always nice. This item can be switched out with Phantom Dancer if your not much for using items, and like the constant increased attack and movement speed.

The Black Cleaver, is also a very nice item, it help with that stupid armor, and with Yi, those 3 stacks will be up in less than 1 second. Of course if that is not a problem, but heroes that keep getting away from you or your not able to get away (Which never should happen) Frozen Mallet is always a nice item to switch this out with.

Last but not least, The Bloodthirster. It increases damage and lifesteal, and it gets better over time. This is a useful item if you're pushing creeps back, or if you're pushing a tower.

Other Useful items.
Banshee's Vail, it is good if against a team with many stuns, since Highlander does not stop stuns, this can help.
Guardian Angel, gives some survivability, and if you do die, you have a second chance at getting away.
Infinity Edge, higher crit chance, and increases the amount of damage crits do, what is there not to like?

At the beginning of the game, by Cloth Armor and a health potion (If you're having trouble you can buy 2 Health Potions). From here go to the Small Golem camp, use Alpha Strike when they show up. If Alpha Strike procs on one of them smite the one it procced on. If it procs on both just smite whichever you want. And if it does not proc on any of them smite one of them and focus it down. A potion can be used here if needed.

Next go to the Wraith camp, use Alpha Strike on the big purple one, if Double Strike is ready use Wuju Style first to make sure to kill them quick. A potion should be used here.

Next go to the Wolf camp, Alpha Strike once again. Once they are dead Recall back to base and buy Long Sword and a Health Potion, if you do not have enough gold for a health potion, just wait as you should have shortly after.

Repeat the steps, going through golems, wraiths and wolves. Recall back again and buy Madred's Claw and a Health Potion. This time go to the Blue Buff Golem, and kill it.

Now you can either continue jungling a bit or you can run around and help in lanes.

I choose this skill sequence as Alpha Strike and Wuju Style helps in the jungle. It is possible to get a point in Meditate earlier, as it does heal you for a small portion of your health, this is completely up to who ever uses this build. Personally I forget to use it, unless if I have time to use it when I'm very low on health. Otherwise I would just run to minions or creeps attack them a bit and I should be at full health with the amount of life steal I have.

The Smite does explain itself. It is used for jungling.

Ghost can be used for chasing or running to a certain place.
This can be replaced by some other Spells

Useful spells:
Flash: A quick way to catch up over walls. Or a good way to get away.
Exhaust: Slows but their movement and attack speed. Useful in 1vs1 situations against a high attack speed player.
Ignite: Extra damage and a good counter against Heal. Though not that useful.
Cleans: Removes any stun that may have been applied. Highlander may stop slows, but it does not stop stuns.

Useless spells:
Heal: No, just simple, no. We don't want that spell, it is useless
Rally: Has annoying ever used that spell?
Clarity: Yi might use a lot of mana, but that will not bother him that much.
Clairvoyance: Yes, you can see where they are, but that is not needed as you will be jumping them.
Fortify: It may increase damage to creeps, and stop damage on towers, but you are not a tank, and if you play right, they will not get close enough for this spell to be useful.
Teleport: It may get you to your minions, but often that will be while your enemies minions are near, which will show them where you are.
Revive: Who is stupid enough to take this. "I just died, I'll revive and charge back in, and die again. FEEDING FOR THE WIN!" *Whines about being killed*

Pros:
High life steal.
Some Survivability.
Good against assassins.
High Armor Penetration
High Cooldown Reduction
Fast

Cons:
Low Health
Low Armor
Stunable

This is a no brain build, it is easy to use and easy to master.

Anyone can use this if they want, it is mainly for myself.
Advice is greatly appreciated if they are positive. Negative advice, trolling and flaming is ignored.
So I don't care if this gets bad or good votes, I just need it for myself.

P.S. If enough will like this build I will make it better with pictures and a movies of how I jungle.