The PvP mode provides arguably the best opportunity to earn nearly unlimited sparks. All that you have to do is go and fight without any boosts (so that you keep going as long as possible) until you lose. After you lose a fight you will get matched up against much easier opponents for a few rounds; fight them and you’ll earn the same kind of spark bonuses that you did initially.
This is also a way to earn a ton of battle points, since you don’t lose battle points when you lose a battle, but you win battle points whenever you are victorious in a battle. Do the win-win-win-lose-win-win-win-lose over and over to farm for battle points, skyrocket your rank in whatever the current event is, and earn high-ranking awards very, very easily.
In order to unlock new elementals you will need to complete the gems in a belt, which is done by winning in the ICL. Before you do so, you can get a sneak preview of the new elementals by looking at the “type” of the creatures in the creature store. In addition to fire, water and plant, you can also unlock rock, then lightning, then wind, then robot, then dragon, then void. Each, of course, has their own specific strengths and weaknesses.
As you add more creature elements, so you will also add more rarities. Rarities are measured in rank from 1, 2, 3 early on in the game, all the way up to stupidly high ranks such as 30 (or XXX).These sky high ranks have nearly unlimited power, but of course once you rank is that high it will take a nearly endless amount of sparks to upgrade it anywhere meaningful.
For extra tough battles, always be sure to consider moves and not just power. Moves can make all of the difference and unlike most monster collection RPGs, even the seemingly not-so-useful buffing and nerfing moves are consequential. A confusion attack or a burn attack will end battles faster due to residual damage and/or attacking one’s own teammates so use them when you have the mana for them.
Go back to old stages and play them as often as you need to for balloons, tags and rewards. Even the easy stages will earn you something but generally, the harder the stage is, the more rewards you’ll earn from beating it.