Hi, I'm MAZZAL1, quite new to this game and actually Silver 3. I'm doing this build guide because I tried it and I can say it functions pretty well! For a more detailed Vayne(/adc) guide refer to http://www.mobafire.com/league-of-legends/build/legendary-mechanics-preseason-1h-tutorial-video-montage-413488 that was really helpful to me! Thx Proxxiii for this guide! Anyway, this is a little deviation from his build...
Critical Combo + Movement Speed
30% crit from Statikk Shiev + 30% from Rapidfire Cannon + 30% from Phantom Dancer + 20% from Infinity Edge = 110% (=100% approximated to max floor) + You do 50% bonus damage from crits + You have Silver Bolts = they will cry a bit...
Did I mention you have 135% bonus attack speed?
Anyway, as an AD Carry, you are meant to survive as you do tons of damage. Reserve a place for one object that will help you in this. You can buy it as last object if you are doing well and and manage to stay alive by yourself, but if you are struggling to survive you may consider to buy it before... Which object you should buy depends on the situation.