[synack]

My first upgrade was pedals. Now my Tiagra shifters are on their way down in the UPS truck. My next upgrade will be a new bike.

[TxCyclist]

Saddle was my first change out. Followed by tires.

[whyeyebike]

My first upgrade was wheels, tires and pedals. Since then, nothing but bar tape and a couple of replacement chains.

[stdu007]

First was a saddle ... second a wheelset, then the chain and a new rear derailleur ... and again and again .... every thing was updated ... except the frame and crank ...

[speed]

wheelset for sure, unless the saddle is really uncomfortable. Most mid to high end bikes have crap stock wheels anyway because bike manufacturers know most people will upgrade to a better wheelset of their prefference, and it helps keep down the cost of the bike.