The first step is to play the game through from start to finish. Try and get as many gems as you can and this should put you some way to earning that last achievement.

Once that's done and you've saved all the inhabitants of Clover Island select the fast travel point on the space station:















Then just smash every box in the room with the fast travel point. This should give you around 150 gems and take less than 20 seconds:













To reset all the boxes you don't even have to travel anywhere. Just use the fast travel point and select the space station again, this resets the boxes and only takes a few seconds to load.















Then just repeat until the achievement pops, it won't take all that long and is pretty easy to do.

I hope this helps.