I would recommend against buying cheap clothing online, especially since sizes for cycling clothing varies so much (moreso than regular clothing). Try clearance racks at your LBS's. If you want to go "generic cheap", try Performance Bike. I wouldn't go cheaper than that, having tried a bunch of crap from KBCyclewerks. I haven't tried eBay knockoff jerseys though, supposedly the quality can be good but seems hit-or-miss.