@Power Play  
I’ve done that. But getting an average of 1 crystal 550 gold and 100 exp from chests still isn’t so fast that I’d turn down getting some extra on the side. A level 30 helps a lot tho, since it makes all challenges until you unlock the level 4 challenges trivial. (Damn Scootaloo and her 4th challenge, I don’t have any yellow over level 9)

@Background Pony #E865  
Or just farm Scootaloo’s second challenge. ;P

@Wiimeiser  
You press on a pony to select it (it will stay selected until you select another one) and then you press on the screen. This will fire 1 or several balls towards the enemy (depending on the level of your pony), these do damage based upon level and matching color type (red does more damage to red, green does more damage to green etc).  
The balls will bounce when they hit a surface or enemy (in a straight line, at an angle from the impact).  
You can fire as much as you want, but you have to destroy the enemy before the clock at the top ticks down and the enemy get an opportunity to attack.  
If you get enough kills your special (the colored liquid under your pony) will power up and allow you to do something good.
 
It’s pretty fun, a heads up if you decide to play is to save all of your crystals and buy the pony pack that costs 100 when you can. This gives you a level 30 pony, which makes progress a lot easier. So don’t waste them on the cheaper 10 or 40 crystal ponies. Also, the first time you complete a challenge you get crystals as a reward, so if offered an ad after beating one for the first time I’d recommend ‘‘watching’’ it to get extra crystals since it’s quite the grind getting them through rng otherwise.

So how does this game work?