I thought i should try out this build and when i did i got great results i fed on the other team so much they surrender most times, I think its good to start off with boots, i chose the berserker greaves because of the movement speed and the attack speed. i then recommend the infinity edge for the high attack damage this will start getting you some kills. you then should get the phantom dancer for the good attack speed/attack damage combo. so then you get the black cleaver for both of these parts because of the attack damage and attack speed boosts.
and so you can stay in the lane longer and increase your damage by even more, get the bloodthirster for the life steal. my final item is the tiamat which is very useful for teamfights and clearing out minions, it also grants you mana and health regen.

I really think that you should use flash and ignite for twitch because flash is good for going through walls, running away or chasing an enemy. the ignite is really good with your passive (Deadly Venom) which continuosly deals damage over 6 seconds, because it will help you finish someone off because of the venom and ingite working together and doing singnificantly increased damage. this is my build i hope you like it :)