Thanks, these spells help here a lot... get that Augment Summoning feat.

And use the variant rules to augment your created undead as well posted in the link above.
If your DM is generous, he will allow you to apply the enhanced attributes to your familiar skeleton warrior. In fact, I believe it's by the rules.
Sadly, the skeleton does not gain feats...
Is there some possibility for an arcane spellcaster to get Desecrate? It's such a nice buffing spell for undead.
Otherwise: Get equipment. Low HD undead can be much stronger if you give them weapons and armors.
Tensers Floating disc helps you to carry some heavy armors and weapons, then Summon your Undead INTO the armors
And you'll find out that a single ghoul or ghast will be much more effective if he's hidden in a group of zombies and skeletons with the same armors.