There are several ways...
- Buy them from the market using game money (clintz).
- Get them from packs by using credits to pay for them.
- Have someone sell one of theirs to you.
- Win one through the daily Cr card lottery.
- Get a very high score in ELO at the end of the week to get a CR.
- Win one in a contest or tournament made by fans.
- A Noel card is given away on Christmas (or about that time.)
- Cards can be won by completing specific missions.
- Legend cards are won by passing a series of missions within a certain amount of time.