Welcome to my Master Yi Build, there are a lot of people who are split between AD Master Yi and AP Master Yi to me Hybrid Yi or Spellsword Yi as I will be refering to him as for the rest of the build is in my opinion on of the best ways to build him.

a few little notes:
1) if you have any questions on about this build just message me on LoL (Riku777) and I will be happy to explain anything to you
2) just remember this is just how I think Spellsword Yi should be built if you have any other suggestions I will be happy to hear them

Pros

[*] Early Game Harass With Alpha Strike
[*] Able to Deal Both Physical and Magic Damage at the same time if used correctly
[*] Jack of All Trades
[*] Can be an Initiator and Soak up damage due to Meditate

Cons

[*] Weak Physically Early Game
[*] Mana Dependant
[*] Hard to Farm if against a Ranged
[*] If CCed During Meditation can Cause your death

Double Strike

Master Yi strikes twice every 7th attack.
The Passive speaks for itself getting a good amount of attack speed 1.4 or greater this becomes very deadly and able to take down squishies very fast and effectivly

Alpha Strike

Master Yi leaps across the battlefield striking up to 4 enemies, dealing 100 / 150 / 200 / 250 / 300 (+100% of ability power) magic damage to each enemy with a 50% chance to deal 260 / 320 / 380 / 440 / 500 bonus magic damage to minions.
With Spellsword Yi this is your initiation, your escape, your pick off this is your bread and butter. DON'T underestimate it's Power, this is what allows you jump onto a prime target and let your auto attacks go to work

Meditate

Master Yi channels, restoring 28 / 56 / 84 / 112 / 140 (+80% of ability power) health every second for 5 seconds for a total of 140 / 280 / 420 / 560 / 700 (+400% of ability power) health. While channeling, Master Yi gains 100 / 150 / 200 / 250 / 300 armor and magic resistance.
This is your recovery after the fight, allowing to initiate a fight get out and heal before jumping back to ro help the team. Just make sure you are far enough away so you don't get CCed while using this skill because it will end Horribly

Wuju Style

Passive: Increases physical damage by 15 / 20 / 25 / 30 / 35.
Active: Master Yi can activate this ability to double its effectiveness for 10 seconds, but this removes the passive bonus until Wuju Style becomes available again.
Wuju Style...This is what defines Master Yi, Spellsword Master Yi or just plain AD Master Yi This is who Master Yi is, passivly Increasing your attack damage to match yourself up to par with any other AD champions you might run across and being able to double for that killing blow that you thought would get away.

Highlander

Increases Master Yi's movement speed by 40% and Attack Speed by 40 / 60 / 80 %, and he becomes immune to all slowing effects for 8 / 10 / 12 seconds. Additionally, killing a champion refreshes all of Master Yi's cooldowns. (Assists reduce half of the base cooldown amount.)
Master Yi's Ultimate this can be so helpful when it comes to a team fight getting an assist can send you right back into the fight and pick off someone else for the process to repeat itself.

Now to go into depth of why I recommended the Runes I did

Greater Seal of Attack Speed: This gives Yi that extra little boost in attack speed needed after Alpha Striking to a prime target.

Greater Mark of Attack Damage: This helps early game since with Spellsword Yi being a Jack of All Trades he can't speciallize in AD or AP so he can be weaker then your other champions early game.

Greater Glyph of Ability Power: This can make up for your lack of early AD damage by making you able to harass with Alpha Strike more Effectivly as well as give that extra boost to Meditate.

Greater Quintessence of Ability Power Greater Quintessence of Attack Speed Greater Quintessence of Attack Damage: I personally Take one of each so my Spellsword Yi isnt trying to specilize in either AP AD or AS but this is all personal Preference

Now let's go over the items
[*] Boots and 3 Health Potion - This is a good start no matter what lane you are going to it's really safe.
[*] Stinger and Fiendish Codex - This is usually what on your first B should bring, turning this into the Nashor's Tooth, which is Spellsword Yi's snowball item, if you get this early gathering the rest of your core items is easy.
[*] Ionian Boots of Lucidity - This is just my personal preference being able to use your skills more often but this is just me.
[*] Kindlegem into the Spirit Visage - This may seem like an odd item on Master Yi but the truth is that 20% increase on your Meditate as well the MR you get from this item helps making you tankier and survive longer in fights against the AP mid.
[*] Sheen and Phage - I prefer to get these at the same time reason is Sheen gives you the mana and ability power to give you a boost and Phage gives you the health and damage to keeping you on track with your opposing AD Champion But in the End its turning into a Trinity Force
[*] Bilgewater Cutlass or Hextech Revolver - The reason I say or here is because at this point you only have room for one or the other my personal preference is the Bilgewater Cutlass because it gives lifesteal which helps when your Meditate is on Cooldown either way you will be turning it into the Hextech Gunblade
[*] Guinsoo's Rageblade- Spellsword Master Yi take complete advantage of this increased attack speed with each strike plus if you fall below 50% you gain extra attack speed as well as spellvamp this is extreamly helpful and making you able to soak up damage as well as being able to still dish out damage

Now to go over Teamwork as well as Laning

Since Spellsword Master Yi is a Jack of All Trades don't be afraid to get your hands dirty and get some assists as well as kills, but remember you're not indestrucible, Your just Master Yi

Top: Spellsword Master Yi can excel in each of the lanes but I feel his best Lane is Top the reason for this is because Top usually is another melee champion so you don't have to worry about being out ranged as well as not having to fear your lanning partner accidently taking a minion or two.
Mid: The next best lane is Mid the same farming that applies to Top works here but you will be up against a ranged AP so you will have to be careful and try not to get to close
Bot:Not the best choice due to the fact you will be against a lot of range so not recommended for people new to Spellsword Yi.
Jungle: Possible but I don't take it and Spellsword Master Yi is really difficult to jungle.

This can be stressful due to the fact that it's hard to last hit against someone ranged, and you want to conserve mana as much as possible in the early levels but don't get frustrated it all comes with practice and determination.

Well this is my guild to Spellsword Master Yi if you have any questions or suggestions just comment or message me and I will try to explain or take into account your suggestion.