If you feel like you're getting behind your enemy with the money-flow. Build a Abyssal Scepter instead of a Hextech Revolver (which then leans towards no Will Of Ancient).

The Guardian Angel is there because if you go into really late game (40+ min) you want to have an advantage in those teamfights , which an extra-life will give you. So I'd sell the Kage's/Deathfire Grasp.

Try to farm as much as possible with your Q. Don't be affraid to hardpush, your Lighting Rush will make you safe when ever they'll try to gank you.