do. not. get. lifesteal. on. twitch.
you should be last hitting early game, not autoattacking to slurp your life back.
on a side note. Unless you're against the rare tank stacked teams (3+ tanks) then you get the Biggest increase in performance the fastest out of either of these 2 build orders:
start with Doran's shield + 1x hp pot
1. Boots of Speed, BF Sword, Cloak of Agility, Infinity Edge, Upgrade boots
2. Avarice Blade, Boots of Speed, Avarice Blade, BF sword -> infinity Edge, Upgrade boots
after that it is adaptive but usually Phantom dancer is the next item to build.
You do not need aspd on twitch, especially early game. Early game you get kills by chasing and plinking off their life in big chunks, followed by a large expunge, not shooting 100missles per second that do no damage giving them plenty of time to return to their tower.
You dont need attackspeed until the game evolves into team battles and you need to blow your damage quickly and reposition before you are focused.