I'm silver 5, been duoing with a gold 3, playing with high silvers low golds and I've been winning my lane ALWAYS.
Cs/trades etc, I've won.
I've took into consideration about freezing lanes / overextending and it's really paid off.
I played 2 games with him, and both I've won lane in kills and in Cs.
First game we lost because lux failed to hit ANYTHING, I was amazed. Not one bind, not one ulti, nothing until they were in our base. She went 0/8 in first 10 minutes.
Second game, everything went well, teamwork was amazing compared to who I get matched with in soloqueue.
I main Vayne aswell, well used to as i don't play LoL much anymore, just jump on for fun
The main serious thing you need as an ADC is the good support, especially on Vayne as Vaynes early is really bad & anything that can boost that while just making her scale even harder into late is a giant game changer.
Find yourself a good support & DuoQ, not just one that plays well, but one that has decent synergy with your own play style, go on skype, get HIM to be your map awareness, so you can concentrate fully on farm if you can get one that knows when to engage, it's even better, means they can make as many plays as you can.
I found myself losing more games purely because the supports i was put with can really pull you down on a vayne, like my last game was with a Fiddle, one of thee most useless supports a Vayne can have, doesn't work with her kit & is a hindrance more than actual help.
I didn't come out terrible as decent play can still pull you through, but having that insane help rather than an insane hindrance is so much better.
Supports I've found work with me, is probably Janna & Lulu.
Janna because her shield is great all round on a Vayne & her Tornado can not only flip people up which is great in itself but if they decide to dodge it the wrong way you can line a condemn up real nice.
Lulu just brings so much, not a support that will get you early kills all the time but it is one that will just maximize the crap out of you mid/late, because she brings insane utility & can keep you alive, even during early so you can farm.
There are more & everything has there weaknesses, probably best to find one that not only suits vayne, but your play style.
Example most, even I will tell you blitz is really bad with a Vayne, as it's a make it or throw it sort of combo, if you both come out on top you'll both crazy scale, but if you don't he'll be like a used tin of Heinz beans :/