I have been playing Vayne since she has came out. And i have tried every near possible build type and here are 3 that have been note worthy.

In this guide I will explain the reasoning behind everything, for every build. I will not be making the guide pretty though. First build is in Green, second in red, third in orange

You can use vayne as either AS/AD. AS Carry. And another build posted for later date(in trial) lots of fun, hard to use.

First The masteries.
---- These are all actually fairly obvious. Giving her Cripple, and Haste just happened to work well with the Trees. She has slight mana problems as an AD/AS route, mainly because of tumbling all the time. giving her more experience will help her reach the tumble cd needed, to constantly get a great boost. As well as giving her a increased buff from Minions. Once blood Razers is purchased, she should have the lizard buff as much as possible. She will dispatch the lizard quite easily.

Now Skill sequence
---- Obviously since we are going AD/AS we need to be boosting both as much as possible. The AS increases will help her passive. and the AD increase gained from tumble is just great. Condemn could be used to simply hit a champ back towards the group.

Next Rune build.
---- Although many people are having a debate about this, mixing AD and AS we require the Armor Pen, AS doesnt help so much in early game since her passive wont actually do that much damage, since every champ is still relatively low health. Armor pen will help not only the early game, but later, since we still want to focus on some of each.

Item Purchases.
---- This is the crux of any build. Synergizing items with the skills of a Champ. We start out with
----Dorans blade, the health, the damage, and the life steal will carry you well in the early game, letting you get last hits easier, as well as harassing.
-Boots of swiftness. In order to ignore getting more movement speed later on or even pretty early. All Vayne needs is the boots of swiftness. Her ult. and Ghost. And the reverse speed item, frozen mallet. instead of getting zerker boots 380 movement speed. she could sit on 410 comfortably. that extra 30 movement speed will allow her ult to scale much better.
----Malady. This cannot be helped, i love cheap AS on her. not only that but it helps your magic champ buddies. does 42 damage damage herself. and reduces magic defenses, further helping madreds razors.
----Frozen Mallet. This item is actually god for Vayne. Her inability to run away effectively will get boosted by this item. By essentially "reverse speed movement bonus". Slowing the enemy down so you don't have to run faster. This also helps make kiting easier. And gives her 20 attack damage and 700 health. This just makes sense.
----Madreds Bloodrazer. Well this makes most sense because of silver bullets, over a period of 3 hits, you essentially do 24 percent of enemy health before armor. We put 1 point in the mastery Archaic Knowledge. Have a malady. Occasionally do 500 damage to minions, making her lane better/get liz buff.
----Black Cleaver. If you so desire get this item earlier. It will get armor pen for ur AD. gives AS, and gives some damage. Getting Black Cleaver this late will make her more of a carry. Getting it early will make her more of a ganker. This is up to you.
----Infinity Edge. This is probably the last item needed, if you arent a fan. get a Trinity. Sell your Doran's Blade if it comes down to the end here.

----Spell choices
Exhaust is for early ganking. well timed exhausts and Condemns will nullify any attempt by the enemy to get near you. or Run away. This is an obvious choice.

Flash or Ghost. These are a tough call to choose between, but i would go with ghost because of its awesome potential to use offensively. If you are stretched out from ur team on the map, this can be used to quickly catch up. I find Flash has a higher chance of escape in times of need. but this is up to you.

Will Add more later

Notes- This is pure AS. Skills to reduce CD on Condemn, hold them in place for longer.
Another note - TUMBLE IS A WASTE The time it takes to get a tumble and 1 shot off. you could have already hit more times Increasing the proc on the weapon items and passive.

Items, Substition possible for Frozen mallet for more survivability. or more AS or Movement speed

Runes, substite more AS, or more Magic Pen. I am not sure which one is better since the bulk of your damage is actually magic.

Play style, Be mid early on. Always focus on creeps. Purchase peices when you can

Not up yet.

The world is not always as civilized as people might think. There are still those who would follow the blackest paths of magic and become corrupted by the darker powers that flow through Runeterra. Shauna Vayne knows this fact well. As a young privileged girl in the heart of Demacia's elite, her father tried to convince her of the constabulary's ever-vigilant eye. Young and nave, she truly believed that her world was one of perfect safety, until one night, when a twisted witch took interest in her father. The malevolent woman overcame her father's conciliar guard, then tortured her family before murdering them. The young Shauna escaped only by hiding herself and then fleeing once the hag had departed, plagued by the screams of her loved ones as she ran. A burning hatred was born in her that day, one that could never be denied.

Vayne was able to take care of herself using her father's money, and she began to train as soon as an instructor would have her as a student. By the time she was a fully grown woman, she had become a grim warrior. However, the fields of battle were not to be her home. Demacia needed a protector, one who hunted those lost to the darkness. Shauna used her family's contacts to become the first Night Hunter, and now her prowess is the stuff of legends. It is said that those who practice the black arts quake when they hear that the Night Hunter is on the prowl. Despite her crusade, Shauna has looked at the League of Legends in horror. There are champions who have clearly lost themselves to the blackest of magics, and who have been embraced within the League even though they should be put down for the safety of all. The time has come for the Night Hunter to execute her secret mission to purge the League of Legends.

Not all shadows are to be feared. At least, if Vayne has her way.