I made a video tutorial with this guide: Your text to link here...I will walk you through everything. Step by step. I have played Master Yi almost every game and I all the details. The only most basic thing I want you to know is that you an assassin, you can't start team fights. You have no Crowd Control so avoid that. Also only build Attack Damage, Critical Strike, and Attack Speed. You are naturally fast so the only things you really need is boots. maybe some other items, i will explain later.
Follow all the runes and masteries.

Before You even start League of Legends. Put 10 Kpop songs on your iphone. If you listen to Kpop you get +1 emotion. I suggest Ailee, Girls Days, EXO. definitely EXO!!!
At the start of the game you want to buy Hunter's Machete and 2 Health Pots and Stealth Ward. All good players use the wards. You wanna smartly place the ward in the area you want to gank. BTW gank means flank in League of League.
Get Red Buff/Blue Buff. that is the blue thing or the red thing. You will need the Health Pots to heal yourself after the Red Buff/blue buff. You want to get Stalker's Blade before the first 5 mintues of the game. try to get Boots too if you can. Now with the Stalker's Blade you are ready to gank. Stalker's Blade lets you slow enemys!! YOU need this!! Do R,Q,E combo if they flash then slow them with your Stalker's Blade. Or flash with them!! Yes you have to get to level 6 before you gank.. sometimes
...sometimes you might have good teammates but i suggest start looking first gank at level 6.
YOU MUST GET at least 1 KILL before the first 10 minutes. This is important !! you must start strong in the first 10 minutes or you might as well quit. Also be smart with your health! after you get Boots of Speed} and [[Stalker's Blade try to get B.F. sword with the money you earned from kills. If all goes well you should get B.F. sword before 15 minutes. Trust me its not hard. Then you must build Statikk Shiv ASAP!!
Now everything should be easy. you can Q,R,E or R,Q,E doesnt matter just build AD critical strike! Follow me on instagram AC130_footwork

just press Q. and learn how to last hit. Not that hard.
Team fights are ehhhhhh...
try to avoid them. You are super squishy. Definitely don't engage a team fight. GET THE F**K BACK!!

Master yi is the best at kill stealing!!!!! press the Q and R E and boom!! 20 kill game! Be selfish. make sure you get your gold!! CARE ABOUT YOUR SELF ONLY . YOUR teammate needs help? nah press R and run for it. Dont feed.