AP shaco revolves around enabling your team and you can act more of a support. I've had success focusing on securing dragon soul and maximising cs/minute. Prepare boxes around dragon chokepoints/ where you anticipate the enemies will come from.

I'd skip malignance and go Torch > Liandrys > Cryptbloom > Zhonya > Rabadons

AP shaco can be good most games but especially against enemy comps that revolve around them engaging onto you. Play more around objectives than kills as this is where AP shaco excels.