There are many other guides of master yi out there, they all suck. I am going to teach you scrubs how to get straight to challenger with this build.

You need the attack speed and the scaling attack damage runes to be a beast late game with high attack speed and damage while the cd reduction and the ability power quints will make you the master mage with high ap burst.

I like to put all my points into offence because i think Master yi benefits from having both attack damage and ability power routes taken.

You need the nashors teeth for maximum hybrid as they give 50 attack speed and 65 ap! This is the best item for a good hybrid Yi. boots of lucidity will give you just the right amount of cool down to spam your E to do the damages.Kindle gem and ruby sight stone will give you enough tankyness and cool down to be the ultimate hybrid tank Yi with an extra morellonomicon your ap,attack speed and cool down reduction will be through the roof!

Maxing your E will give you just the right amount of damage to 1 shot all the minions and give you tons of farm while getting your q next will make you a mobile killer. your heal is not important and should not be gotten until late game as you don't need a silly heal.

Because of not getting your meditate until late game you should get clarity and heal as clarity will let you spam your moves more because of your insane cdr and your heal can sustain you early game while your meditate can sustain you late game.

During a teem fight you should alpha strike in when your team is half dead as the enemy team should be half dead at that point too giving you easy kills. You use your E in the middle of the fight and ult around and win.

You will encounter no problems while in mid lane or any lane as master yi will just shrug off all attacks with his kindle gem. Any damage that does get though you could just heal it back up so laning should be a breeze.If you are losing lane go to another lane and let your team mates take care of the problem.