I find Vayne one of the MOST difficult adc's to play, if not the MOST.
-- Laning phase is almost assured to get you killed if you're new with her.
-- CSing is SO hard due to her short range.
-- You get poked so much, even by like lucian and other short range adc's, and can't trade nearly enough pre 6 without extremely good positioning.
-- Her condemn has to be a split second decision, and aimed correctly, or it's a waste with a long cd that's heavily mana expensive.
In addition, to team fight with her, you also need to MASTER advanced techniques.
-- You MUST be able to orbwalk, even with high attack speed, and alternate it with her Q to kite or chase.
-- You MUST be able to time your q to not only make maximum use of your ultimate, but also dodge skill shots.
-- You MUST have a front line to protect you. Your one escape is condemn. If its down, you're probably dead if caught out (unless you're super ahead). While this isn't an advanced technique, positioning with your team is, so it sorta counts. LOL.
I've seen some vayne players 1v5. And I've also seen some so bad they nearly lost a duel to a bronze cait. And everything in between.
She's really tough to master, but once you do, you're practically a god.
Sadly, I don't think I know anyone that's a high level vayne expert (maybe Vayne Hentai below, if his namesake is accurate) so I don't know who to refer you to, except maybe to watch some of the diamond games in the client, see if you can find one that's playing vayne.
-T