I have a spell to summon the ancestral ghost and a scroll to summon a skeleton, but is there more? And if so how do I do it?

http://www.uesp.net/wiki/Morrowind:Conjuration_Spells of all the Conjuration spells in the game.
They have the info (NPC name & location) on where to purchase the spells.

If you bribe, admire or charm the spell merchant a bit, the prices should become more affordable.

If you go to Balmora you can get conjure weapons and a Skeleton.

Get a levitation spell or potion, then take a boat to http:///www.uesp.net/wiki/Morrowind:Tel_Branora.

Up in the tower is a guy who sells all sorts of the best Summon spells, but I think you have to levitate to get to him.

OK, thanks guys.