Wild Cards I: Amazon.co.uk: Martin, George R. R.: 9780765394880: Books
Wild Cards eBook : Martin, George R.R.: Amazon.co.uk: Kindle Store
Wild Cards: Card Sharks (Wild Cards: New Cycle Trilogy) - Martin, George R. R.: 9780671721596 - AbeBooks
GURPS Wild Cards - Wikipedia
Wild Cards - Metacritic
You can't convert any of your common wild cards to elite ones unless you have all commons at level 14 (probably same for other rarities) : r/ClashRoyale