20-40 zombies should be plenty. Plus I'd say 15-20 for skellies/ghouls if you take the blood line power.
Plus with zombies/skellies you can always model the extras as emerging from the grave, just get some extra bases and use up all those bits! It'll save you some money. Personally, from a thematic point of a view, I recommend all your "starting" zombies and skeletons should be "full bodied" just as if they had been raised well before battle. It looks better, and it also really helps sell the "raised" feel of the new stuff.
Though if you play at 3k+ you may want to add A LOT more than what has been recommended, just to warn you.
Though, locally (especially in casual games) we tend to use dice to represent the extra. If we need to check for charges we just place some on that side to see if they'd hit. However while in tournaments some might be ok with that, I would not count on it.