For those who are having troubles at farming: just no matter what champ you go, if you suck at farming, just take AD runes until you learn how to last hit. What's the point of extra ability power or hp if you are getting outfarmed by your opponent a lot? After you learn how to auto attack with extra ad, remove one ad rune (from 15ad to 13ad +3ap or so) and try again. With every match you will become better and after all you can do it with zero extra ad.
You can say: wtf, how I will do dmg or how I will tank that guy? Simple, if you get +~30 more cs before minute 10 than before, it is worth. You will buy better item than you could buy before runes swape and after all you can also AUTO ATTACK enemy when you don't attack any minion with your EXTRA AD. Just practise. When laning, you should get 70+ cs before 10 minute mark, otherwise just listen to my tip.