IIRC one does not find the ring of wizardry, one gets it made. As for the uses, the "wizardry" part would seem to imply something like 'give your mage additional spellcasting slots'
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The last arrow of Legolas kindled in the air as it flew,
and plunged burning into the heart of a great wolf-chieftain.
All the others fled. -J.R.R. Tolkien, The Lord of the Rings