How to return from a long slumber.

[Assur]

Like I said, first Raise Skeleton, then Mastery. Not only you get more Skeletons earlier this way, but they improve also better in early stage when Raise Skeleton itself is pushed instead of Mastery.
Of course goal is maxing out both, on the long run it doesn't matter anymore.

IIRC the people over at the Necro forum of the AB workrd out that the optimal setup for a Summoner is to put one point in Skeleton Mastery for every three points in Raise Skeleton.