I think its gonna look amazing as a staff on your back whilst you cast your spells. In my mind i imagine this "glow effect" to be white energy being sucked in from around the caster, whirling round the head of the staff until the centre gem explodes and a beam of white light hits your foe.
"The three Nazgûl continue to swoop down onto the riders. As Shadowfax charges into the thick of the battle, Gandalf raises his white staff above his head, and as he does so, a blinding beam of white light comes from its tip. With a shriek, the Nazgûl draw back, then take to the skies. "