Welcome to the Ap Yi anti meta gaming play style trust me before you even start trying this you will be raged at and called a troll almost every time you do it. Now i play Yi as an anti bot, Now you may be wounder OMG WTF BBQ what a NOOOOB but hear me out if you play this right u completely shut out there ad carry and support now that's two members of the enemy team that poses little to no threat, in this guide i will talk about skill set up, items and how to use them, runes, and lane partners. Lets begin shall we.

For runes I take flat magic pen Reds Flat Ap seals and Quints and % CD reduction Glyphs this is aimed at keeping your damg steady and constantly flowing through out the laning and team fight phases.

For Masteries I take a 9-0-21 set, maxing out cooldown's Damg boosters and money increasing stats, because AP Yi is more or less COMPLETELY Aplha Strike based you need to have it up when ever you can to keep pumping out your scary damg, so cooldown's will insure this happens when you need it so your not running around like an idiot while it's on cooldown, items also help with this maxing your cooldown reduction to the highest point at 40%, That being said your Alpha Strike will come up every 3 sec's at max lvl and cooldown.

For items i start with either a Doran's ring or an Amp tome, this is situational depending on your lane partner if your forced to manage your own mana take a Doran's ring, but if not the amp tome gets you a super Quick lucky pick ;) witch starts your money down the right path to get your items sooner, now because most of the time your CS will be the highest on your team you will have some extra money to spare when you go back for items i highly recommend you buy a Pot of Brilliance it will give you a sizable Ap boost as well as CDR witch is the point of AP yi, from tho's items finish your MET(Morelle's evil tome) and sorc boots, after witch the build is situational I will say you should get your CAP(Rabadon's death cap) after this but DFG(Deathfire's grasp) is a close second, so when there out of the way you want to continue your dmg out put with LICH BANE and ABYSSAL SCEPTER

In this build Your focus is on ALPHA STRIKE and MEDITATE so max them when ever you can completely disregard WUJU STYLE because the AD has no place in the build until later, of course take your HIGHLANDER whenever possible it will help you stay in range for your attacks.

For summoner spells I take IGNITE and FLASH for obvious reasons you mite get tired of a enemy slipping away with super low health after your attacks so ignite is a quick finish that will secure a pesky kill, were as flash will always be helpful for closing gaps and quick get away's.
yes there are other skills that can be useful but there two just shine above all the others. Of course the choice is up to you.

Tactics with AP yi are simple DO NOT target enemy champ's unless you know you can Sucre a kill because more times then not you will get yourself killed, the way to harass and you can even do so under the tower is to target the closest minion to the enemy that way you will show up where that minion was rather then on top of a retreating enemy leaving you valuable to CC and tower aggro, as long as you can do this you will continually harass the enemy while farming CS, not a bad deal right, for advance tactics id just say there's a glitch with yi that if you alpha strike a dying minion and it dies before you hit it you will return to the place you were before you used the skill it may not seem like much but if u can land it you will be one happy yi

In lane you really want a good support who can ward and keep you running on full cylinders which i'm talking about soraka she can heal give mana lower enemy mag res give you armor and silence, shes a walking battery for master yi because of his healing she can focus her effort and mana on harass and self healing, giving you mana when needed you cannot stop this lane!

PROS
+insane laning power
+the ability to harass from complete safety
+will completely shut down and ad carry if played right
+Surprising tanking ability with meditate
+great at cleaning up in team fights
+makes bot lane rage when they cant keep up to you with your damg and cs
+super fun to play

CONS
-can be mana hungry without soraka as his partner
-after alpha strike your are rendered useless
-while meditanking easily stopped by stuns or ignite
-monotonousness