It seems like you can't walk through a mall these days without someone trying to check out your nails. You know what I mean, right? All you're trying to do is go get an Auntie Anne's pretzel, when you're accosted by a mall-kiosk clerk with a magical $50 buffing system. The good news about those kits is that they do make fingernails look glossy without polish. The better news: you can get the same results on your own without shelling out so much money.
All you need is a buffer like this one ($2.99). Be sure to use a buffer made for shine, not a nail shaper or file. Follow the directions on the package, but usually you'll have a two-step process: buff with one side, then follow with another to create shine. It's best to buff in one direction, with a light hand. (Going gangbusters on your nails won't make them any shinier, and you could wear the nail down. Ouch.) After you've achieved the shine you want, apply hand cream or cuticle oil for extra moisture.
If you've never done this before, try it. You'll be surprised by how shiny your natural nails can be, and you'll also be able to fend off the kiosk people by flashing your hands.