I might have to post my own guide on Yi. Yi is really only powerful when he has the "late game" items, but I managed to get a bloodthirster and infinity edge in less than 25 minutes.

Of course I took this build off someone I played with. I kept playing with Yi ever since.

I absolutely love this guide, using it as a starter when I first started playing Yi, it helped me a lot, especially learning the mechanics of the game, as without it I probably never would've realized how valuable a neutral creep buff really is!

In public games, 75-80% of the time I end up heavily carrying my team through mid-game ganks and backdooring, usually accumulating atleast a 1.5 KDR, (over 3.0 in my last game, 21-6), and I find the ability to adapt from this guide amazing. I've changed the item build quite a bit, shying away from crits and more onto atk speed and life steal.

Lately, my typical game and item build has been as follows:
Long Sword + Health Pot
Pill back for Madred's Razor + Vampiric Scepter (Sound familiar?)
Jungle for Lizard Buff
Attempt ganks and help out lanes.
Get boots of choice, if there are disablers, get Mercury's, if not, Swiftness.
Work towards Phantom Dancer (Zeal first, Sword of Divine if Jax is giving you trouble)
Work towards BloodThirster or the Aura one (forget name D: )
This is where you choose what you need, if you're having trouble with bulk, get SunFire Cloak (Warmogs if it is really THAT bad, but you shouldn't be the one that's tanking), spell bulk? Banshee's Veil. Usually games don't last this long for me, but if so, I've usually been fed enough to get Infinity Edge, if I'm not doing well, I figure out why and choose the item to remedy it.

Just of note: Armor Penetration Marks are more effective than Critical Damage marks unless you're working a very high critical rate (even at 50%, APen is better). And even when you do get to that high of a crit rate, the Armor Penetration is effective for the entire game instead of just when you reach that point.

Just tried a couple of games using this guide. That was my first time playing as Yi. It was quite successful. The first game ended too quickly with the enemy surrendering, but the second game I went 22/4/10.

However, I noticed that without the golem buff I'd be constantly OOM and need to go back to base because there are no mana items in the item build and Yi's abilities cost a lot of mana. A few of those deaths I had no mana to use his Ult even though it was available.

Sometimes someone noob teammate would see me killing the golem and decide to "help" me out, and end up last hitting and stealing the buff. GRRR.

When jungling, do you go for all the neutrals on just your side of the map? If that's the case, do they regen fast enough for good exp compared to laning? I tried jungling a couple of times but always found myself underleveled.