We consider the WBC gear a great way to show off your national pride. Check out this great spring/fall jacket. If you're from Mexico, or have family in Mexico it is pretty hard to beat a hat like this. A friend of mine with a unique sense of style and a flavor for all things Dutch couldn't resist this monstrosity, which he actually might be able to pull off.
All in all, don't go overboard. But much of this gear can compliment the stuff you already wear to the game - or it might just be something a bit different than your run of the mill gear you see most of the year.