Black Edition is pretty picky with cards but Silver seems it’ll use anything
http://gopro.com/support/articles/software-update-release
Faster cards will however give faster transfer back to your PC, if your PC is up to the job.
MyMemory is a good seller, I have 2 of these, work great with my Black
http://www.mymemory.co.uk/Micro-SDHC/Lexar/Lexar-32GB-High-Speed-Micro-SDHC-Card-600x-Class-10-UHS-1-90MB_s-with-Reader-
Or any of these in Class 10 or Class 1 UHS (speed filter on the left)
http://www.mymemory.co.uk/Micro-SD
Rather than 1 big card I’d recommend 2 smaller ones. A battery will run out before a 32GB card, one in the camera, one in the reader so less chance of leaving it at home and can work out cheaper (when I got mine 64GB was more than 2x a 32GB).