sup m8s, I'm Phluxzr, I have ~600 Vayne games and this is a guide to playing her

Vayne has one of the weakest laning phases in the game. Her condemn is her only defensive ability, her range is very short and she is prone to losing very hard to lane bullies. Coming out ahead in the laning phase is difficult vs. good AD carries. Generally you want to play safe, using your Q (Tumble) to dodge any skillshots or to harrass. V

Generally once you get your core items (BOTRK + AS item) you want to start split pushing. Unless there is an assassin on their team such as Zed and Leblanc you can generally 1v1 anybody on their team with these items. You want to swap out to the blue trinket to get vision on objectives such as Dragon if you think the enemy team are attempting to do it.

The general rule for teamfighting is to autoattack the closest target to you, unless you can get autos off on a priority target. Make sure to utilise all possible tumbles when you have your ultimate active. Generally once you are full build you will 3/4 shot squishy targets with enough crits.