Elemental skill and Magic accuracy both only affect the accuracy of your spell.
INT boosts your dmg and your magic accuracy, depending on the mob, 1INT = 0.5macc or 1macc. Until the point where you have 10 more INT than the mob you'r fighting, 1INT give 1macc, after that point it's just 0.5macc.
MAB only boost your dmg.
NQ Elemental staffs give +20 macc and 10% increase in dmg.
HQ Elemental staffs give +30 macc and 15% increase in dmg.