Weapons and armour can be sacrificed. Not sure what level you are, but if you are high lvl, just do the next two quests for easy favour.
The better lvl the equipment you sacrifice, the more favour. It can be a true waste though, spending a 10 gold item for about 250 favour.
But the second and third line miracles are quite good most of the time, nice back-up spells.
Also, there are degrees of altars too, the better the altar, the less you need to spend on favour to get a miracle. Crafted ones I believe are better than the first one you get.
Edited, Aug 22nd 2007 11:43:09pm by Zieveraar