You're browsing the GameFAQs Message Boards as a guest. Sign Up for free (or Log In if you already have an account) to be able to post messages, change how messages are displayed, and view media in posts.
Nintendo Power mentions that "skillful" play will reward players with the game's currency. I'm not certain if this is alluding to achievements or simply playing well in matches, but the rest of the sentence mentions nothing of Invasion mode, so I think it's safe to assume that playing Invasion mode is not the only method to obtaining coins.
Remember those in prison as if you were their fellow prisoners, and those who are mistreated as if you yourselves were suffering. Hebrew 13:3 (NIV)