This is my Vayne guide.

we pick the highest possible offensive stats from red and quints and thus is armorpen red and ad quints.

early armor to handle the auto poke from both the support and ad carry

lategame you will have weak MR and the late mr will almost dubble it.

Standard offensive 21 9 with crit and no ignite

You will be weak early until you get the Stattik shiv so farm it out then you will be very strong through out the game

Since damage was buffed and attackspeed nerfed in season 3 we buy lots of dmg and that scales good with the q