Game's not that interesting, just making a few notes.
Grinding in a puzzle game is bogus, but—
Apart from the weekly Meowth special stage the only good one is
It doesn't seem so great initially, but the trick is to be strategic with how you make matches so that you move the coins over to the right edge. Five will appear in total including the three at the start. The amount of bonus coins you get from matching them increases exponentially the more coins you match (match three coins = 100, four = 300, five = 500), so shoot for a four or even five coin match.
Excluding special stages like Victini and Eevee.
Helpful notes on passing challenges