Well, lets start shall we.
Everybody in LoL calls Master Yi a Noob Champion but I will make you believe in a different story.
He is one tough Son of a 'B to kill when he has this build in his manners.
Mostly its just because its hard to get kills with him in low level and in early game.
But its easier when you first grind and then attack.

Keeper of the ancient art of Wuju, Master Yi is a mystical warrior from the isle of Ionia. He descended from one of the few tribes dedicated to the preservation of Wuju, a martial art founded with the principles of absolute spiritual awareness of one's self and one's enemy. When the armies of Noxus invaded Ionia, Master Yi joined in the Ionian defense to fight the craven enemy, bringing his village honor through his unparalleled mastery of the blade. The ensuing battles ravaged the land, but no conflict inflicted as much horror as the day the armies of Noxus closed in on Yi's village. Left undefended, the village became the unfortunate test subject of the latest invention by an up-and-coming chemist, now known as Singed. The remains of the village that Master Yi returned to were so horrific that it remains a festering scar on Ionian history. To this day, no Ionian will ever publicly speak of what occurred.

After the Noxian invasion was contained, Master Yi fell into a deep isolation. For years, he trained morning to night, speaking to no one and refusing offers of consolation by fellow Ionians. The only thing stopping him from madly charging into Noxus battle lines headfirst was his pledge to keep the Wuju style alive. Even though he seethed with impatience, his rage became a tool for sharpening his practice of Wuju, developing stronger and deadlier skills for his eventual vengeance. The only thing that roused him was news of the League's formation, and Noxus's subsequent enrollment in the League. Master Yi now brings his mastery of the blade to the League of Legends with unflinching purpose: to avenge his kinfolk and end the predations of the Noxus once and for all.

Well, mostly if you engage a champion immediatly at lvl 1 Maters Yi will get ganked like it was his worst nightmare.
That's why you actually need to try and not get in touch with any champion untill you are level 6, Why level 6? Because then you whave your ULT, and you will be actually be a great damage dealer. Unless you have a **** build made out of Armor stacking and that will get you nowhere the only thing it will get you is being called noob and laughed at.
Ok when you are at level 6 and you have someone at your side it will be easy but mostly he always needs to assist you untill you have your Wriggle's Lantern, Mercury's Threads and Phantom Dancer.
At that point its just good damage and you will be fast and tough, but not tough yet.
You need to know how to use your abilities. There is a sequence in how to do start your abilities to get the most damage.
At first you need to make sure a Champion of the enemy team is not close to one of his/her own turret.
After that you Start: Highlander(Ultimate/R)& Wujustyle(E) And you need to run as fast as you can towards your enemy, then you will need to alpha strike him and trow Exhaust(D or F) so he/she will be slown down and you can do you last damage to get your kill. mostly this works but you need to keep paying attention to other enemies close by at ALL TIMES

Master Yi has some various pros and cons which will be stated here.

Pros:

• Great Pusher/Turret Killer/Destoyer
• Fast Farmer
• Easy to learn
• Great escaper/chase mech
• Hist Ultimate(Highlander)gives you a CD reset when killing someone(45% Change when making an assist)

Cons:

• Vulnerable to disables like: Blind, Stun, Exhaust etc
• Low overall Hp but will be taken care off in later levels
• Not so great when along a team, Mostly faster and will kill steal. so beware people will get mad

These are some of my matches that I won with Master Yi
Yes I know that i am only level 10, but I did alot of owning during the matches and these are my last 4 matches that I intended (at the time I am making this build guide)

I want to thank Zoki for his Guide it teached me alot,[/color] if you want to know more about the Abilities or the Runes picked in this guide please read his guide on that: here

I learned alot of this guide. I also learned how it would fit the fighting style I presented you in the chapter : "How to start".
But Zoki's Guide wasn't 100% working for me so i edited alot of it.
and this is the most fitting for me.

Thank you for reading this guide and I hope it helps.