Digital Jedi is right about the runes, but this guide isn't useless.
Avarice blades are horrible, just take them out of your build. They take 25 minutes to get 750 gold back, and if you resell that's still half the time = over 12 minutes.
Change your Crit Damage runes to either Crit Chance or Armor Pen (Depending on your other heroes, as both rune pages together can be costly) and it'll fare much better.
Build Phantom Dancer as it outclasses Yoomu even with the active (other than movement speed wise) but don't get two of them, as you'll do more damage with pure damage rather than crit at rates higher than 60-70%.
New Black Cleaver before or after Phantom Dancer. It's just beast.

Build useless, check enclosed link :
http://www.leagueoflegends.com/board/showthread.php?t=70173
Why No One Should Ever Buy Crit DMG
Conclusion:
Don't ever buy Crit DMG runes. If you want to get Crit DMG, get Armor Penetration instead.

Hey pretty nice build i tryed i got 20/3/10 +1 from me :)

Nice build, but why more then 100% crit chance? That is jsut a waste of gold, you should skip one Item (maybe Executioner's Calling) for Malady or something. You get nearly the same lifesteal, 50% AS. I also would change the Crit Damage Marks & Quints with Armor Penetration. +1 from me