Dont worry about reposting, a mod will be able to move it soon. Its just supposed to be in the Necron forum, and not Necron Army Lists.
As for the Question, id say two units would be nicer, large ones, 6-10. However id look at prioritising Destroyers and Wraiths in some cases, so sometimes you may only get to use one unit.
Scarabs should be out second Core choice, along with a Flayed One statline fighter as the third. Would be nice, with both being 0-1 per Warrior unit taken.