Why another guide to ??? I don't know, I build her a bit different than the guides I've read. My main focus is AS... More shots = more DMG (and more crit's).
I'm not gonna write all the stuff you can just as well read in the other good guides. I'll focus on the stuff I do in my build that I havn't read in the guides I used.

I go with ArPen and AS. The ArPen is just plain nice, those big buff tanks will run away screaming when you shred their armor! AS is, as I mentioned, my main focus so i stack that up as well.
Greater Mark of Desolation and Greater Quintessence of Desolation because their amount of ArPen is too good to pass along.
and because I want that AS very high. This will also give me that much more DMG output in the early lvl's.

Nothing new here, I use a pretty basic 21-0-9 focusing on DMG, mana, movement speed and that extra buff time. This will come in handy when you grab that blue buff for max usage.

Start of with and 3 x . This will get you going in the early lane. I usually wait untill I have about 1100 g's before I go to back.
Buy and . Now you have a little more DMG output and that scepter will help with your survivabillity, at this point I'm usually finished with the pot's and I'm relying on the scepter to keep me alive.
Now when I have about 1200 g I go back for the . After that I finish up my and then I build .
At this point I have my basic build wich can take me a long way.
Whenever I come back to the shop i build .
Here's what I like to do in the late game. I want that AS maximised so I go for wich give me a nice 50% AS and also a 25% CR wich I also enjoy. At the same time you get mana regen for your .
If the farming is bad I normally stop at and begin building after that. is IMO a great late-game item for , giving me some DMG abd splash DMG but also extra regen for your . In the late game there's usually a bit growded in either end of the map and that splash DMG is good for clearing out some mobs and getting some kills or assists. You could go for another for more crit chance and AS but at this point in the game I really apreciate that splash DMG and regen. Plus it can be hard to find those last 800 g sometimes.

You wanna max out that W as fast as possible. The priority should be R>W>Q>E. I only spent that one point in E because it's good for brush-checking.

Always go for that Dash'n'Flash! You don't wanna miss a kill because you are lacking speed at that critical moment and you don't wanna get caught in front of an agry mob without the means to get away.

I'm never jungeling, other champions do that way beter than so let them. I'm going for that occational blue buff when I feel short of mana for that .

Farm farm farm! is suplime at killing minions, you can take them down i stacks. Minions are one of the biggest gold-sources when I play. Getting below 100 minions in a game can really reduce your chances of getting the item build you want.

Nothing more to say... See you in-game!

Oh.. BTW the actual attack DMG with masteries and a fully buffed will be 339,6 and not 287,6.
Your AS will have a small increase due to .
You will also have 23% lifesteal with and fully buffed .