Tips for vayne

Your CS is really bad. Not just on Vayne but on every champion you play.

I'd recommend trying to focus on last hitting the minions. You should try to get all of them in every wave.

In your settings, Hot Keys>Player movement> , player attack move click, change it to key “A”. In fightings, press A backwards, and your character will automatically attack the closet target while moving back. Also, use Q to dodge abilities. E ability takes practice, but basically use it only when you can stun them to the wall, or you're eager to push him back. Use ult+Q to get away from danger. That's all i know, im not very good at vayne too

OH and what should i build shiv or phantom?

Well, looks like your a new player I'm not sure if Vayne is the right champ for you. Please take no offence as i dont mean any to you. Not only if Vayne weak during her laning phase. She is the hardest adc to master along side draven. I recommend you just focus on learning the game a bit first though trial and error in normals for now.

Things you need to improve are alot of things, cs score, lane management, how to receive ganks properly, map awareness, how to work with your support, team fighting and your role as a marksmen. ETC.