I just bought Vayne yesterday, and of the many questions I have about her the biggest is what is more effective on her when deciding on attack speed or lifesteal. The way I see it is that lifesteal synergizes well with her Q, while attack speed is more geared toward her E. While I understand its largely situation dependant, some insight to her would be awesome as I think her mechanics are pretty hard and I'de like to improve as quickly as possible. Thanks
Why bother choosing when Blade of the Ruined King gives all 3 AND self peel?
attack speed makes autos faster, which means that your animations are faster, which means that you can kite better, which means that your damage is actually higher than if you had ad items because you aren't dead because you can kite.
vayne doesn't scale with ad very much, but her kit is much better with attack speed, unlike graves.
Your main items on Vayne are going to be: bork, boots, phantom dancer (more AS, crit, and sweet movement speed), last whisper (believe it or not, most of her damage is actually physical. You don't want to over-rely on her W). The last two items differ from game to game I believe, but many people tend to go for Infinity Edge of AD and stronger crits, and then a last defensive item (can be GA, can be scimitar, banshees, hell even spirit visage or bloodthirster. It really depends).
So in other words, get bork first and then attack speed. Lifesteal can wait.
If you farm well I usually build vayne like this
Starting items
First back (1400+ gold)
x2
First back (Less than 1400)
x2
Buy 
after your support has 
and 
as needed
Build then finish
After that I almost always get (
gives a bit more burst and is cheaper, this is a preference buy on which you want)
Then 
(defensive) or (offensive)
At this point your build should look something similar to this
Defensive:
Aggresive:
I recommend rounding your build out with a and some kind of defensive item.
If you really need more damage pick up or , whichever you didn't get earlier.
I highly, highly recommend considering 
for general damage and tankiness.
for dealing with abilities you can't cleanse, such as 
Spear, 
/
Hook, 
Pull/Ultimate.
-> 
against abilities such as 
Charm or other CC that needs to be removed.
Feel free to pick up as your third or fourth (after finishing or ) If you are facing CC that is hurting your ability to teamfight. DO NOT UPGRADE IT UNTIL YOU ARE FULL BUILD, IS VERY GOLD INEFFICIENT FOR DAMAGE.
In teamfights your main priority should be getting as many attacks off as possible, 
does heavy amounts of true damage to tanks and combined with your you can melt tanks. It's A-OK to focus a tank down but damaging a carry is more important IF IT'S SAFE
To get more to the point, the highest sustained dps build looks something like
Single target tankbuster:
Burst assassin:
Recommended:
If you're looking to really learn what vayne is capable of I would highly recommend watching this you can find the whole game here Imp is one of the best vayne players in the world and really showcases the champions strengths.
Good luck on your adventure into the wonderful world of Vayne
always rush
