The standard build is to begin with Bloodrazor and Berserker's Greaves, then pick up Guinsoo's Rageblade and Blade of the Ruined King, and then finish with Bloodthirster and Death's Dance .
However you can swap Bloodthirster or Death's Dance for Ravenous Hydra if you feel like Hydra works better with you ..
Usually late game, I swap Bloodrazor for Spirit Visage to increase the healing from my Lifesteal and give me a bit more HP, and the Mage Resist is always nice against mages who try to use CC to stop you ..
and Phantom Dancer is an option if you want more Attack Speed.

My Runes are Extremely Debatable.. however I do like to really put my best into making the build actually Full Lifesteal and Attack Speed and use every bit of bonus I can get into the build to make sure I offer the absolute maximum ... :D
The one Crit rune is there just in case you get into a sticky situation, you never know, that one percent Crit chance may actually save your life.

Masteries follow the same idea of the Runes .. Getting the Absolute maximum Attack Speed and Lifesteal so you can call this a true "Full LifeSteal and Attack speed Yi build"

In many other cases you will see people max E before Q and that's normal, but i just like to get my Q on lowest Cooldown since you need it in dodging 90% of the opponents skillshots, and sometimes, even after they land (Fizz ult)

But i Just want to point out that maxing E first is absolutely Ok and its really up to you and I can sum it up like this :

if you feel like ganking that Morgana is impossible with the 2 hour long binding, you can put some points into your Q and next time she tries to stun you, jump on her with your Q.

However if you're not having any problems like the one mentioned above (your team is not feeding :D) you probably should max E first since it gives you much more damage when maxed.