This is the one I've played the most of out of the 6 or so I've rated so far. I made it to level 12 on my longest run. The strategy is interesting, both in the turn-by-turn play and in the shaping of your deck. Early on, having as many units as possible seems to be key, otherwise you run out; and therefore cheap packs of basic units are great. Late game, unit quality is king since you can only play one per turn.
The early game is pretty rough because of the shop RNG. On the rounds you most desperately need more units, the shop might not offer you anything you can afford. I lost early several times before I got a good run.
Archers seem to be bugged, in that when they reach the end of the lane they don't throw themselves into the enemy gems like other units do. Though this sort of adds to the strategy; you can treat lanes with enemy archers as safe and avoid putting your own archers into empty lanes.