Cool! I'm presuming you're from the USA. If you don't have one, do buy a USA football shirt. The new blue away shirt looks really cool btw
http://www.footyheadlines.com/2014/12/nike-usa-2015-away-kit.html?m=1

It doesn't matter that it's a european cup, having a shirt will be a conversation opener, and it really is the accoutrement de rigueur.