Unique Motion Sprites
One of the things I find most frustrating in this game is when something happens and I don't understand why. My mana or creatures seem to mysteriously disappear, or the opponent happens to spawn ten token creatures all of a sudden. I know many people complain about bugs in this game (and I know there are some), but I think many times I find myself mistaking a bug for a card action that I didn't notice.
So to help people better understand and realize a card mechanic that has gone off, I think there should be some more unique motion sprites. Right now, the only thing I notice is a little white glowing star trail that moves from a support to a creature or planeswalker. While this is helpful, I think it would be more beneficial if each of these effects looked different. Power-ups glow yellow, debuffs glow purple, food token change green, something that makes each effect seem more unique and noticeable.