When should I raise my focus and self, instead of putting xp directly into magic skills?
Raising focus and self also raises every magic skill by focus+self/4 (those you haven’t trained yet will benefit when you do train them). So, raising either focus or self by 4 points is like putting 1 point into each of the four schools. Mana conversion, the other essential mage skill, is also raised, by focus+self/6. There are two paths characters generally take – raise all skills equally, or raise one or two to a target level. If you want to advance all your skills at the same general rate, you would spend xp like this: raise focus twice, raise self twice, raise each of the four schools once; every third time, raise mana conversion twice. If you’re advancing only one school, then when you put four points into focus and self, put one into just that school; rinse and repeat.