There's nothing much to say. Master Yi is like a Bruce Lee with a sword, and he can with "lucky slot " enter to fight with his cosmiiic AD.If the situation is kind of hard i mean,if you have hard opponents in alley ,then its better to get more experience in skill calling "Meditation", and then you don't have to come back to ur "home" as usually as You've done before. Use a punch calling "Alpha" in group war. And a "style Wuju" – Good one in Jungle and farmimg.

-Also if your opponents in alley are AD Carr'ies, High experience in Meditation will make u more immortal in alley and you'll get faster levels than them.
-On a first minutes of game "Style Wuju" will make u faster in killing minions.
-Use punch "Alpha"on a minion next to you, and You'll be safe after finished attack.

-Meditation its better choice to heal your dagames in game, but Master Yi is susceptible on traps in a first minutes of game.
-If Master Yi tries to farm, by using "Style Wuju", attack him few times,to make him use "Meditation".
-One more thing, if u cant make kind of slower Master Yi it doesn't mean that u can't stop him.Obviously you can, by using Ultimate skill.

- Flash - Its good to escape, to get someone, susceptible in team fights. This one skill always had to accompany Master Yi
- Heal - In normal fights is always important. A lot of players usually forgets about that, u have the healing spell,but if you will use this spell as smart as you can,it will give u dominance at the start of the game. For me its a second skill,which I'm using when i play as a Master Yi, becouse of one thing, Master doesn't have too much health, and usually this skill is reducing that big defect.
- Ignite - Very susceptible when you are killing someone. Use it to finish your opponent