You can't put requirements on the skills themselves beyond what level is needed to cast them. If someone learns a skill, they can use it as much as they want (even the 'arrow skills' if learned via scripting).
That being said, you *can* make it so that items cast skills when used, like scrolls. This is how the arrow skills work if I remember correctly. In the item template window, for the OnUse action add the cast skill option. Then you could have a crafting combination to create the item.
...You know, I think it could be possible to have some sort of DnD style magic system, where you can prep spells to use before battle. You could make it so that items when used, teach the skill, and when the skill is used it causes the skill to be forgotten. If you're really wanting to, you could set it up so that multiple components need to be used to learn the one-shot skill.
