When you are playing as vayne in the bottomlane you have to know that in early game you have to focus on your farming. a main rule for adc's is that you should have around 70cs or higher at 10 min then you know you are farming great.
my experience with Vayne is that you need to have your mechanics working cuz if you can't do your mechanics good enogh you will lose.

When your farming as Vayne you only use your Tumble to last hit the big minions cuz they are the most importent of all minions if u miss the big one u have to practice your CS cuz if you can't CS you can't Adc thats the main rule.

When your team get into a teamfight your job is to come in last! REMEMBER THAT! The way you can come into the fights is to use Final Hour then Tumble in so u get invisible for 1 sec and focus the one on the enemy team that is the strongest then u just go on to the next and remember to use your tumble cuz it gives your more dmg to basic att it's importent and when Final Hour is on you get invisible and that can help you escape too if u lose the fight

Teamwork with Vayne is easy enogh, your team just need one there can give Vayne movement speed like lulu Zelian Janna and Nami they can boost your passive Night Hunter that give youu movement speed when you are near an enemy and Final Hour gives you more movement speed when it's activated