Only worry about rarities once you're trying to get your perfect equipments. Which is a LONG time from now.
IIRC, 0-7 are Legendary, 8-31 is Rare, 32-255 Normal. Rare items are stronger than Normals, and Legendaries are stronger than Rare. The best equipments are Legendary only, if it's the same as in D1 & D2.
Rarity matching (as in, the same number) gives even more boosts when equipped together.
For starters though, I'd just steal any item that says new if you're a perfectionist.
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Chant the name of BlAcK TuRtLe, winner of the 2010 Guru Challenge!
NEXT TIME!