The most detailed and best Vayne Build, Runes & Counters Guide for bottom Vayne on LoL Patch 14.19 are found on LoLalytics.
All in all, BotRK is a WAY better item on Vayne, at least in my opinion and seemingly on pro player's mind as well. The "optimal" core build for Vayne would so happen to be BotRK, Greaves, PH, IE and LW, their pick order depending on how the matchup goes and with an optional...