1. Our current throwbacks look the best, so that's the style of jersey I would suggest.
2. Avoid current players, no matter what they're contract is. You don't want to have a Losman or McGahee jersey you just payed $75 for sitting in the closet.
3. I would suggest getting a player that is a little different. Having a Kelly Jersey is cool, having a Jack Kemp jersey is even better. (I have both BTW, although the Kelly was on sale for $31)
I would suggest players like:
Tom Sestak (#70, best DT in team history)
Jack Kemp (#15)
Cookie Gilchrist (#34)
Can't go wrong with any of those IMO, and you'll probably get a few compliments when wearing them.