The spellbook potions are temporary stat boost potions, which do not require any ingredients. You can make as many potions as you wish, one at a time. However, you can make stronger potions yourself (and do it faster), with easily gotten ingredients.
There is a unique permanent potion, which Allan would want for his second quest if you had picked him (though you can still drink it yourself, if you don't mind leaving that quest incomplete). Since you have Barbatos as an alchemist, there isn't any problem using it for the...