Spiders are size 6, so be sure to saddle up with wine bags
I guess a little chaff might be useful versus heavy cavalry, to absorb the lances.
As for black servants, I suggest a dragon helm over BS helm (fire protection) and something that gives strength (e.g. girdle of might) too boost their life drain. By default, it is pretty weak.
Personally, I don't use them, though - too fragile with their low HP. By the time they have 20+ protection they are no longer cheap.