Real AD carrys just destroy tower farm and shout with your suport and jungle (but just into they cry you don't have to be mean) and makes team fights funny, because you will just see a lot of guys taking damage until die just because they wanted to focus you ,what a joke what a joke your are twitch .TIPE YOU CAN ALWAYS USE AMBUSH Ambush TO RUN IF THE TINGS JUST DONT GOT HOW YOU WANT IT OR TO START A GANK WITH THE DAMAGE BONUS
I DON'T PUT THE FINAL 2 ITENS BY PURPOSE DETAILS ON ITEM SECTION BELOW

it´s simple W Venom Cask make slow ( a little but makes0 but more important make the targets hited get 2 stacks for your passive Deadly Venom and E because when you use it on a champ with 5 stacks(maximum stacks) of you passive Deadly Venom make your kill guarente or your skill point back =)

Well first the start itens
some people are more confortable and familiare with Boots and 3x Health Potion
but because of your passive Deadly Venom the choice of Dagger and 2x Health Potion is kind of a way to steal the first blood from your enemy making this star itens the smartest for twitch Twitch.
Anoter smart choice would be Doran's Blade
P.s.I'm not discarding the choice of Boots and 3x Health Potion It's the best choice for begginers players that are not familiare with Twitch and he's playing style
In your first way back to base
If you follow my structions and with luck and skills you got the 400 gold extra from the first blood in this cause in should come back in lane with an berseker berseker's graves, otherwise you should get an boots Boots and a few potions in the case your support sucks if you have an taric Taric or a sona Sona forget the potions and go for the kills and farm.If you got lucky and your jungle is helping you and you got some kills if you have more than 1400 gold you shoul make a zeal Zeal and Boots in should enter in mid game with your B.F. ready
Mid gameMID GAME
In mid gam you should have you phantom dancer Phantom Dancer and you infinity edge Infinity Edge ready for the team battles try to make anothet phanthom damege for you crit chance be more than 95.4 % than you make bloodthister The Bloodthister( some people like to make it before phantom or infinty edge is an option I dont prefer this but its ways up to you )
LATE GAMELATE GAME
I like to make an Runnas Runna´s Hurricane because give you more attack spped and have a great passive for late farm and further team fights and than another bloodthister The Bloodthister
OPTINAL ITENS
Guardian Angel Its a very good item when you're support its just a ******
Black Cleaver its makes your bruise much better good item
Banshee's Veil good item when AP dudes are really making mad
put on discussions some itens you aproved for the rat

Make you have more damage and speed a simple masteries that works pretty good with all AD carrys

It's just to make sure when you have your build complete you going to have 100% of crit damage and more damage and speed of attack

Twich is the most powerful early game AD CARRY and if that dont convice you he is a rat that which can be inviseble every 16 sec
I am sorry for my inglish but I am a Brasilian guy soo some words are hard for me I really hope that I helped you guys please say your opnion and share some experience in the discussions please dont forget rating =) (please dont say words that in lol would be ****) And this is my first posting please don't care about the editing errors