Yo the names Pseyecho and I main support and I've noticed the Vaynes I play with struggle against ryze or a bot lane with some sort of magic damage with no long range harass and short range disengages it is extremely hard for this champ. After reading her abilities her W seems to be what should be focused on so making attack speed the most valued stat. So I decided to work out a build that gave Vayne early game mag res but still played to her strengths, also adding some extra damage from on hit effects will make her a brutal trading monster.

R>W>Q>E
As get ult when you can, but max W first since this build will giving you plenty of attack speed for procs, then Q because who doesn't like extra damage, and E last because it is more of a utility.

Pros:
+ Great sustained damage
+ Potential for burst with Blade of the Ruined King and Ghost Blade actives on single target.
+ Great split push with Ghost blade active takes turrets very fast.
+ With Wits End, BoTRK, Black Cleaver, and her W can melt tanks very fast.
+ Wits End offers more protection from mages that try to burst you.

Cons:
- Hard very early
- Will require some peel from your team
- Being able to get decent cs a must
- Dont expect to 1v1 any fed zeds lol

Well this is my build, off to league to try it out :) I'll post scores as soon as I can. If you decide to try it out message me your results would love to hear. And as any build, its a work in progress expect updates.