Master yi is one of the best Dps, Carries in The league of legends. Master yi can and usually does turn into the descider of the game. Being able to power throught 3v1, 4v1, or even 5v1 ganks. This makes Master Yi one of the most used Characters in The League of legends And one of the Deadliest if used by the right person. And with such a simple skill set it isnt hard to be the right person.

Pros:
Awsome Carry
Alot of kills
Easy
Simple
Powerful
FUN!!!
Cons:
Squishy early game
weak against tanks and Crowd Controls
A pain if you mess up your items or skill sequences

For runes I recommend Greater Mark of Desolation and Greater Quintessence of Desolation because This gives yi A little more of an edge against Tanks and other DPS characters.
With the adding a bit of dodge this offers a bit more safety in the Early game
With the this offers Master yi some leverage in the early game.

The reason i chose to put The as a first item is the movement speed is descent and the Atk speed is good durring the early game
The reason i put 2 infront of the is because in the Early to Early Mid game you need to beable to put as much damage as possible to help carry you throughthe game and the Life steal is helpful when you have the Attack speed.
After the 2 Phantom Dancers you will need for the additional Damgae and Crit chance and the increse in Crit Damage
After the you want to sell the and get one more

could be used to make your Master Yi tanky and alot harder to kill and is good if against a team of 2+ tanks depending on how your kill record is

can be good if you are against tanks or high powered DPS characters like Lee Sin or Xin Zhao not to mention the Attack speed is nice and the damage adds a good boost

con be useful if playing against high powered DPS or tanks such as Twitch or Rammus

is great when playing with champions such as Nocturne and helps both you and them

Farming is Very Imprtant to Master Yi in the Early and Mid game. Using is an easy way to farm

For summoner spells i like to use to have the ability to get in or out of battle

i use in early and mid game to secure kills and usually using this spell and can also give first blood a huge advantage with Master yi

Master yi is very weak in the Early game. It is best to begin laning with a Tank such as Taric or Sion and jumping in and out of the action securing minion kills and even though it isn't looked nicely upon Kill stealing can help you ensure a better Mid or Late Game. Farming in the early game is important in building up Master yi and building his item build ASAP. You may find yourself recalling alot, and thats perfectly ok, but you dont want to fall behind on your levels (getting a few Health Potion may help with laning)

This is when Master yi begins to shine. This is when you start to become a force against your enemy team. Here Ganking is encouraged but dont get greedy. Having atleast part of your build done here helps with team fight taking some hits and dealing alot of damage with you and your team taking apart the enemy. Beware of crowd controls (mainly supressions, Stuns and fears) for these can be deadly against you. Team fights breaking out you could be a good initiator and a heavy damage dealer. For taking out Enemys quickly or dealing alot of damage please refer to the "Yi Combo"

During the End Game is when Master Yi shows how unstopable he can be. As a Carry the end game is his best area. Here Master yi is picking apart the enemy turrets, and inhibitors. Using the "yi combo" correctly during this time can break apart a 4v1 or even a 5v1. Master yi right now is a power house DPS and For the most part the Back bone of the team being able to push through the enemy team with ease. After finishing the build i always take joy in watching the endless crits over the enemy. This is your spotlight kill as many of the enemy as you can as fast as you can. Again dont get greedy but if theres a time to be greedy its in your best interest to go for it.

This combo is extremely simple

you start of getting to your enemy using Alpha Strike then using Wuju Style and Highlander to chase and destroy your enemy. And with the kill and free cooldown reset just do it again.

Simple but effective