Though some will be more effort to do (others more expensive), a Black Mage wanting to be the best he can be will want to go ahead and at the very least get all the Magic Damage staves (barring Light, since BLM gets no native light nukes outside of Luminohelix), as well as the Lightning Acc (for Stun), Dark Acc (for Sleep) and Ice Acc (for Bind, etc). For a more modest, more commonplace approach, doing the Fire, Ice, and Lightning Damage, and Lightning and Dark Acc would be pretty decent choices.
If you plan on doing other Mage jobs, you may want to look into doing some of the other Elemental Acc staves as well.
My thoughts and reviews
Lady Jinte wrote:
Vlorsutes' Negotiation Skill rises 0.2 points
Vlorsutes' Observant Parent Skill rises 0.3 points
Vlorsutes' Argument Diffusing Skill rises 0.1 points
on all sorts of sci-fi stuff...and things.