Where to spend my AP?

So what the title says, is there some guide to help me spend my AP more efficiently on each class? Currently am leveling GLA and MRD, and I am guessing I should just throw everything at Vitality, but is it true? And is it so simple of a pick to spend my points on any class?

GLA - VIT
MRD - STR

For tank you can't go wrong with vit. You can change then later to str later as required dependant if your play style and what your doing in game. Each class has their respective attribute for example bard and ninja dex healers mnd , blm int

Yes, it is that simple (except for ACN -- they have to chose between INT and MND depending on SCH or SMN use/ preference). MRD can go STR, but all VIT is probably better while leveling and nobody's going to question it ever.