i just answered this, and my post disappeared after I submitted it!
First thing, use a ball point, not a regular tipped needle. Also, do not use a straight stitch. If your machine has a "stretch stitch," use that. If not, set a zigzag stitch that is barely a zigzag, with a short stitich width and slightly longer stitch length. Those two things should enable you to sew jersey without trouble. You don't NEED a special foot. However, if you happen to have a "walking foot," use that; it will feed both layers perfectly together and makes sewing any kind of knits easy as pie. Like I said, a ball point needle, a stretch or slight zigzag stitch, and a regular foot will do the job just fine, though. Good luck!