I have an update on Angry Birds Epic! I've come up with a new strategy and restarted the game.
The premium currency in the game is golden coins. You want to get them, so you can buy the top-level equipment. As a rough estimate, the "golden coins only" equipment is 40% better than the equipment you get normally.
The downside is that all the equipment you get is tied directly to the level you're at, when you receive it. In other words, whenever you level up, your equipment becomes outdated. All level-ups are 10% across the board, so equipment doesn't become outdated too quickly, but still. Unless you're at the maximum level, 25, it's somewhat pointless to get the best equipment.
To get the premium currency, you either have to pay real money or win a daily battle.
My new strategy is to not progress through the game. I stopped as soon as possible, and now the only thing I do is fight the daily battle. Since I'm at the very beginning of the game, the daily battle is ridiculously easy. After all, I only have one character, who can't do any moves besides "attack".
I'll keep this up, until I get, I dunno, 300 gold coins or something. Then I'll go back to playing the game like normal.