I'd roll with:
HQ 1: Necron Overlord
TROOPS 1: 10 Necron Warriors w/ Ghost Ark
TROOPS 2: 10 Necron Warriors
TROOPS 3: 12 Necron Warriors
FA1: 5 Canoptek Scarab Swarms
+ Whatever you have left up to the points value your playing
If you get another
HQ model I would run the Retirbution Phalanx + a
CAD of whatever you have left