I have stopped earning coins through regular gameplay. Is there a cap on the amount of coins I can earn?
There is a daily cap to the number of coins that an individual can earn through Battle Mode wins, and that cap is 400 coins. Players earn coins for each Solo Battle or Ranked Versus Battle (multiplayer) win in Battle Mode. Additionally, players earn a 20 coin bonus with their first Ranked Versus Battle win each day. This bonus does not count toward the daily cap of 400 coins. Coins earned in Story Mode or from Skill Quests do not count toward the daily cap either.
If you do reach the daily cap you can still continue to play Solo or Ranked Versus Battles, but you will not earn any coins this way until the next day. For the purposes of determining when a day starts or ends, the game clock is based on Coordinated Universal Time (UTC).