Ok, I found a way to spam money. Money is what you need to make this game easier, not hearts.
Ok, go to he mewoth stage. His stage starts with 3 coins and you have eight turns to beat him.
You must start by trying to get the coins on the right to get close together. They should be vertical, so you should have an "oreo". Coin on top, pokemon in the middle, coin on the bottom.
Then try and get the coin on the left to either get on either the top or bottom coin of the oreo. Do not try and make a 3 coin match yet.
After about 4-5 turns, meowth will drop another coin. Now make a 4 coin match. Then put meowth to sleep.
If you do this right, you'll end up with 330 coins after the match. If you only do a three coin match, youll get just 130 coins.
Do this for every 5 heart reload, you'll end up with 1650 more coins every reload. If you do that every day maybe 3 times a day, thats 5050 coins per day. More if you are vigilant.
Coins are the lifesavers in his game. They allow you to buy disruption delays, added moves for S ranks, and so on. Crystals will nice, are not needed nor are hearts. You need money, money is more helpful.
Hope this helps.