Due to Orianna's lane dominance ability and low Q mana cost, she can poke her enemies to death pretty easily.
All you have to do is stay behind, farm and push the lane using your Q and W sometimes.
Use your E to gain a shield that might sometimes save your life.
You should use your R in teamfights or to one-shot non-tank target with Q and W combined together.
Also you can use it to make the top laner run away from you. It works, trust me.
If you have pushed enought, you can teleport to other lanes since you are higher lvl than other players.