Thank you! I definitely need to add some kind of tutorial. I'm glad you're enjoying it!
The strategy I used to end up with the high score in the screenshots was to pick cards with a second card in the chord present, but leaving at least one card in each pile to maximize choices as the game continues. There's definitely luck involved in the initial shuffle. All four chord types have either 3 or 4 half steps between each note, so once you get one chord, your best bet is to keep chaining chords of varying types so you don't use up all the same notes, breaking the chain.