This is the build I usually run when I play vayne in ranked play. It usually works pretty well for me, but you may wanna change an item or 2 depending on the situation and the champs you are fighting but this is a good all around build for me. I start off with a dorans blade and tumble and just try to last hit and farm up for boots. Once you get your boots you are a great champ to gank with. You should have your E ability and lead off a fight with tumble and try to get in position to stun them into a wall with your E. A bloodthirster is a must have item for her since she is so squishy. Seriously one of the squishiest champs in the game. Keep leveling up your W and once you get a phantom dancer your attack speed will be high enough that your silver shots alone will do great damage. I usually get a banshees veil to help against stuns and other cc, one good stun and if a couple champs focus you, you are done for. Finish it up with black cleaver and IE. Hope this helps!