try to harras your opponent on toplane with torment and ya bird.
go for last hit, usually use autohits so harras but be care of minions (minions op!)
wait for junglers gank start your wombo combo with e-q so you slow him and do dmg over time than set your w (try sometimes in custom game to aim, its a bit hard), turn on ulti and ignite let jungler an assist as usually :p
if he die push to turret go back get 2 dorans, wards and pots and back to lane.

early you're kind of squeshy, until you get catalyst protector (awesome sustane), so better stay def and wait for help.
if you play vs an ad get frozen heart early and ifyou play vs ap is abyssal cept helpfull (aura items and teamplay are the key to win)
later if you're kind of tanky you can open teamfights with your ulti and hit many enemie with your w.

you also can build Rabadons instead of Sunfire cape,
or switch sunfire so banshees vale if they have more caster than ads

you also can use flash/ignite,
flash/exhaust, flash/clarity and ghost/exhaust