-Summoner spells, Take flash or Ghost (I prefer flash) maybe a heal if your support doesn't have one.
-Q!!!! Tumble is great for dodging skill-shots like Lux/Morgana bind or Orianna's balls... (Takes some practice)
-Make sure you have good positioning, Positioning is EVERYTHING so think about where you are.
-Never initiate team fights...that's your tanks job.
-Consider grabbing a Frozen Mallet. With a Phantom Dancer, I.E and Frozen mallet you have good attack speed for kiteing which means you can escape from sticky situations: Ult>Tumble>Auto-attack, gives you nice distance as well as slowing the enemy. Continuing to kite allows you to take less damage as well as keeping them slowed. If it's a 1v1 fight and you get them low enough to kill then turn to kill but remember you're RANGED so don't go balls deep till the kill can be secured.
-Boots...I sometimes like to grab Boots of swiftness when you've finished your build you'll hopefully have a phantom dancer or two...so there is your attack speed which means you don't really need berserker's greaves. With Boots of Swiftness+Passive+P.D+Frozen Mallet you have amazing kiteing capabilities. When you press R no one can escape and YOU GET KILLS!!
Hoped this helped
Back to my classwork now :/