Hello , Welcome to My Build I hope you'll enjoy playing with it.
First of all I'm cant speak English very well so forgive me if I'm wrong.
I'll shortly talk about why I choose these Runes,Masteries, Items, Skill Seq,Sum. Spells
and a littl summary in the end.

So Why I choose the crit damage?!

-Firstly , I used to play with Shaco a lot from the beginning of the game so It's one of my favorite rune pages what I've just tried out. When I started to buy some crit stuff like Phantom Dancer , Infinity Edge. I saw that I can cause a very very big damage even bigger then
the 300% trinity. So when I reached the 5th rank of my "W" spell and when I started shooting
somebody it's just died in no time , like alistar used his ultimate and died in 5 hit, with 1,9 attack speed .

This is the best way to maximalize the output damage.

I'm bilding cirt strike/damage/atck speed becuse of the "W" Spell . If you buy your panthom dancer infinity edge you'll see that it does an insane amount of damage then I choose banshees
for a littl defence from spells and + health so it was a good way to survive.
After it if u want to maximalize the damage output from your W spell go and build the madred.
it gives you attack speed , +(- x% from the max life), and damage too. So it was my longest game
when i reached this build . So I jsut hope trinity will be good at the end to maximalize your mov. speed and dmg output.

So Firtsly I go for the "Q" spell . it's very good to chase,run and hit exspecially in early game on mid lane. Then I go for the "W" spell this is the core of this build it does an insane amount of damage that makes every enemy to run what is useless against the Chaser Vayne.
I maximalize the "E" spell last. because it isnt a big damage it just good to stun or even to run from somebody by knocking him back.

This is a Hard Choice. Choosing a Summoner Spell always depends on the summoner .
Why I choose the flash and ignite? I choose the flash to run away from late game teamfights
and shoot down every enemy from outside the battle. I choose ignite because combined with your
AUTO HIT->Ignite->"E"-> Autohit in early game at half or low hp it can kill everybody so it's a good way to be feeded.

Your unique skills are : 1. As I said AUTO HIT->Ignite->"E"-> Autohit
( this is a good way to kill in early game)
2. Your Ultimate And "Q" => Stealth
(This combo is very important if u want to kill an enemy go press your ultiamte and use the "Q" to get colse to his as much as you can. Use your "E" spell to knock him back and make him unable to run away and shoot him down :) )
3. Just a littl thing to mention. Dont forget to hit 3 Times an enemy
to make a very big amount of damage this is a must. if u chase you are always faster so you can easily shoot 3 times before he got back under his turret. then keep doing this and use the firts combo when you think that he's in enought hp to kill with the combo. )

Before Voting that this isnt a good guide please leave comment. I'll try to answer asap.
I think I wrote everything so read it carefully and sry for my bad english.
Thank you and I wish u'll enjoy this. :)

Have a day with full of win ;D,
3R17