Both magic skills give up to a 33% discount on eitr- and in the case of blood magic, hp.

at lvl 100 blood magic, the raiser only costs 67 eitr to summon a skele

Some good news at least, is that if you already have a Kill pit for grey dwarves, you can modify it for a shooting gallery and have two archer skeles just pick away at the greys to level you up in a controlled environment, you get blood magic exp each time one of your skeles land a hit, and having a campfire nearby will boost the exp gain by 50% as long as you are well rested. once you have a gallery set up, you can pop some eitr food to summon a pair of skeles( and use a butcher knife to remove any melee until you have two archers and then scoot them up to where they can see the greys and they'll get to work. The skeles do not expire, and last until their HP is depleted, which is mitigated quite a bit if you make the aforementioned gallery. also, if you feel like staying engaged in this process, you can also use the protection staff to keep them shielded, but that doesn't gain blood magic exp quite as effectively, but it will safe guard your skeles against the periodic thrown rock.