Hey there, my first build on Mobafire and wanted it to be on my favorite champion Vayne the Night Hunter. There are TONS of different builds out there for her but here I will show you the way i build her. (read through the whole thing before voting please :) ty)

Alright well Vayne is one of the (IMO) most fun champions out there and I've played her since day 1 of her release. Her early game harass with her Q (Tumble) really tells those squishy enemies your the boss of the lane. And her late game with her W (Silver bolts) makes tanks like Shen and Ramus cry as well as allowing you to deal most of any targets health with a few attacks.

Pros:

Vayne has great early game damage with her Q and isn't too mana reliant unless you are spamming her abilities.
She does tons of damage to tanks and can easily execute squishy champions as well.
She is a great chaser thanks to her passive and she is very hard to pin down in team fights if you tumble whenever you can with your ultimate.
She is a great ganker thanks to her W letting you pin targets against walls (Note: also pins targets to walls, inhibs, turrets alive and destroyed, Jar's ult friend or foe, trundle's wall, anivs wall, and basically anything that makes terrain.)

Cons:
She is a VERY squishy champion and even though you have a stealth remember that will not save your life and playing too aggressively early can hurt you very badly.
KNOW YOUR LIMITS i can't stress this enough, if your laning against 2 melee or even mid against an Annie remember the enemy's abilities, remember if they see u harassing too much they will jump on you when they see an opening when you have over extended and remember you can be melted very easily against anyone with a stun be very careful around morgs, annie, ryze etc.
She does not have that many self sustaining abilities and can cause you to be reliant on your team to keep you in lane.
She isn't very great against multiple targets, i will go more in depth on all this later in the guide.

Flash: Basically has every use out there, chasing running going over walls it really is the 1 spell i say you must get every time with Vayne.
Exhaust: This really allows you to secure that kill on the runners or every shut down the enemy carry in team fights land it on the most fed enemy just to help your team. (THEY WILL THANK YOU WHEN THEY LIVE)
Ignite: Also viable on Vayne but honestly its only use is last hitting which you should have no problems with because your passive allows you to catch nearly anyone.
Ghost: I've seen quite a few vaynes getting this... DONT your ult with passive lets you catch anyone and if you need it to run use your Q and E then even flash if you need to.

Ya I know all offensive not much sustaining runes. Honestly i think armor/MR runes are completely useless. They help early but if your taking that much damage that you need them to survive i think your doing something wrong. Also Mana Per Sec runes really aren't worth it on Vayne either, tumble doesn't take too much mana and unless you are using Condemn whenever you can you shouldn't be running out at all.

I take these runes because they give me great harass with that crit every once in a while which will really scare the enemy squishy and possibly even give you a nice surprise kill. :)

These Masteries are standard and you will find nearly the same on every vayne build. The 21 offense because the only way to play her is AD carry. You shouldn't need anything in Defense because you aren't a tank at all and will get lifesteal to sustain you. So put your last points into mana/health regen and all that nice stuff. I also take the 1 point in 1 gold every ten seconds because she has no farming ability, she is great at last hitting but it really will help you in the end trust me. :)

Ok here is where we get to the good stuff. First of all the build i listed farther up the screen IS NOT my final build at all! If your a good player you defiantly know the same build can't work against every team you fight. Such as if your playing Galio you want Banshee's Veil so it helps your passive but your against all AD and Tanks so its completely useless, and a thornmail will be far better for you even if you dont get your bonus ap from your passive.

I have to say take a Doran's Blade every single time regardless of who you are playing against. Bonus health damage and tiny bits of lifesteal are the best you can hope for in a starting item.

Next move on to a Vampiric Scepter which will sustain you in lane for a while. Next either move onto either a boots of speed or dagger which ever you can afford first. You will turn this into Berserker's Grieves instantly.

Follow that up with another dagger giving you enough attack speed to farm up minions easy enough with Silver bolts.

Now you will want to save up for a B.F. sword, continue to farm or if your team is starting to gank and push a single lane go with them to hopefully get assists or even better yet kills.

Ok here is where smarts come into play. If its a slow game not much ganking not alot of teamfights and everyone is still just farming in their lanes this is where you must be the smarter player. If you get all the items above early great job thats perfect. But now you have a choice if your enemies are mostly tanky not very squishy i recommend getting a black cleaver before bloodthirster. It is one of the 2 tank banes and it helps you farm minions far better than nearly any other item out there. But if you are laning against squishys who use burst damage or combos get bloodthirster. After a skirmish you can heal right up on minions and bloodthirster gives tons of AD for your Q.

Ok now whichever item you didn't get previously get now. If you got bloodthirster first get black cleaver now, if you got black cleaver get bloodthirster. Getting both of these early make you a nearly unstoppable force on the battlefield.

Next gun for a Zeal and phantom dancer.

Alright here comes another smart move where the better and smarter players shine... If you are crushing face getting tons of money i would get an infinity edge which goes hand in hand with your phantom dancer. If the enemy team is more tanky go for a madreds, if both sides are nearly even go in for another phantom.

Your final item- (Besides getting potions and oracles)
This i would personally make a defensive item, either a thornmail if the enemies are AD a Banshee's if they have tons of CC and magic or just a general good item a Guardian angel.

Finish off your build with potions and oracles if you have all your items and were smart by itemizing correctly against the enemies congrats you officially own face now.

Alright this is nearly equally as important as your item choices. I Grab her Q first followed up by her W then next her E. After you have 1 of each BE THE SMARTER PLAYER. If you are in lane against a singed/garen or other tank level up her W more yes i said it her W!!!! If you are against squishy champions go for more into her Q so you rely more on a quick burst than then crushing your enemies health over a period of time.

Vayne isn't just a Q spam everyone levels this up first but honestly doing 30-40 extra damage at level 4 against a tank who will regenerate that by sitting back for a few seconds wont be as much of a long term affect as doing the total damage to their health.

Vayne is great at last hitting simply hit a minion twice wait for it to get low and hit it again. Or use your Q then click a minion that is about to die and boom your farming. Simple as that.

Here is where the fun stuff starts. Because you are so squishy DO NOT EVER start a fight you will get smashed and you will die. In 1v1 fights if they happen for you play smart like always. If they are melee use your E when they get close and Q when they get back in range to hit you. If they are a AP nuker use your ult Q walk right up to them while they can't see you and E them into the wall then burst them down and laugh.

In team fights once a fight has started use your ultimate go for the most deadly enemy champion they have, yet make sure they are squishy enough so you can kill them. Of course use your E on them to knock them into a wall if the moment presents itself and use your Q for a quick stealth whenever possible to stop enemy retaliation. (Although with Silver bolts Vayne excels at owning tanks killing the enemy squishy carry is farm more important.)

Thank you for reading the guide i hope i helped some players into thinking outside the box in itemizing correctly... i see this problem all the time. I also hope I gave you a better understanding of how to play Vayne :) Happy hunting summoners.

Ty for reading.