If you like raping little yordles in the night then this guide is for you.
If you enjoy carry's in my opinion most important role of the game then shauna vayne is perfect.
this is my first guide though i am pretty experienced in the art of raping. good luck.

PROS
•Condemn can be used to escape and kill.
•Vayne does extreme damage fighting one champion.
•Tumble can be used to avoid skillshots.
•Vayne is very good at chasing with her passive speed boost, ulti and tumble.
•Silver bolts is good for farming.
•Tumble can be very effective being chased, tumble backwards and shoot repeat to kill.

CONS
•Vayne is uneffective early game.
•Vayne is fairly squishy.
•Vayne can accidently KS very easily enraging teammates
•Tumble cannot avoid most skills(lock ons)

Ghost-Your Champion ignores unit collision and moves 27% faster for 10 seconds. buffed from masteries. a great ganking escape for vayne.

Heal-Restores 75 + (lvl x 25) Health to your Champion and 50% of that to nearby allies. All targets healed will have a 50% reduction in heal amount from other summoner heal spells for 35 secs. effective for staying in lane as well as escaping and surviving turret diving.

Alternative: Teleport-After 4 seconds, teleports your champion to target friendly minion or turret. 3 minute cooldown if cancelled. Great for returning to lane fast after healing or buying, or joining team fights.

with the fast attack speed of this build you can either last hit or if pushing silver bolts is effective.

the point of the rune build is to give her some extra attack damage aswell as armor pen, but most importantly attack speed for dealing massive damage. also her regular speed is pretty slow.
the experience quints are for staying above everyone in lvl because as i said before she is fairly uneffective early game.

The point of 22/1/7 is for vayne to dish out massive damage with the mana to do so aswell as making both summoner skills more effective and helpful.

the boots are for attack speed an alternate is boots of speed if you think you need that extra speed. the rest for attack speed, move speed, and critical. you also need some lifesteal either
bloodthirster if fed or wriggles if youre having trouble.

in a team fight you can use condemn to help your team. and just attack weak champs using tumble and silver bolts to focus one at a time.

Overall vayne is an extremely effective powerful champ if you follow this guide.