you'd need a turntable with a built-in preamp to plug it into a speaker. Up to a point, the more money you spend, the better, but if you're playing through ipod speakers, any belt-drive turntable would be fine. any 'usb' turntable will have a preamp on it already so it's plug and play.
My personal rec would be to find a tech 1200mk2 (should be about 200-300 on craigslist), which is direct drive but solidly built, add a cork slipmat (20ish bucks) bellari vp 130 tube pre-amp (300) or vp29(70) and then a decent set of powered speakers. 300-500 all in for a setup that'll last you forever, unlike the 150$ setups from urban outfitters that fall apart after a year or two.
and... just did a quick search on a budget kit. turntable lab has this for 300 bucks, and it has everything you need to be up and listening. http://turntablelab.com/collections/turntable-listening-packages-alpha/products/audio-technica-at-lp60-turntable-audioengine-a2-speaker-package-1