Starting out is alot of fun but as you progress, it's impossible to get ahead without spending money, and I mean serious money. The algorithm is set heavily in favor of the game. IE: any bundle you purchase offers a minimum and maximum; coins, cards, junk, etc. 95% of the time you'll get the bare minimum (10 - 100, you'll get 10). I'm at level 54 and it's going to take months of daily play to level up enough to pass a single battle! And as you level up, the same battles get harder too. No fun