You can not learn the Healing spell until you reach level 15. The Summon Ghost spell can be learned on level 1.
If you have a couple free skill points, you can put them into Mana Efficiency. In D2:ED with my warrior I maxed it (level 5) so I could summon the creature and have enough mana left over to be able to use the Healing spell if I needed to. In DKS with my ranger I boosted it enough (level 6) that I didn't need to increase spirit or intelligence for my ranger (especially once I started getting armour with 2 enchantment slots, so could use Increased Mana in addition to Life Line).
