All Western PA referees are expected to act and to look professional. You will need to obtain a referee uniform and should begin with a yellow USSF shirt, all-black shorts, three-striped black socks and black shoes (do not have to be turf or cleated, that’s your decision).
You will need a watch with count-down/up timer, whistle and yellow/red card wallet. As you complete matches, you can add to your kit (flags, additional shirts and other accessories).
There are a number of local and national vendors, here are two, http://www.officialsports.com/ and http://www.officiallysports.com.