New Necron Player: What to Get?

I've just gotten into 40k and have picked up a Start Collecting Necrons box, some more warriors to combine with the ones in the start collecting box to get the unit up to 20, and a Ghost Ark. I was planning on picking up a Cryptek and 10 Immortals as well.

What are some other solid units I should look into? Also, what is the opinion on Destroyers/Heavy Destroyers?