Twitch is an ADC that is amazing throughout the game especially in lane and early-mid game. He can carry amazingly and gets fed if you have just 15 kills.

As Twitch you'll love getting a bit of AD in every type of rune. So you'll start amazingly early game and you'll probably finish the game extremely fed.

For items you should have a lot of attack speed to add more Deadly Venom stacks. You should also have tons of damage with your Items and Runes. Resulting in a Twitchy Twitch.

For spells take Flash, Ignite,Teleport or Heal.