Gems are too expensive and coins are useless if there is nothing to spend them on

This is a great game, however, once everything is upgraded and all outfits are purchased, there is nothing to spend coins picked up or received. Given that the gems are too expensive, how about using coins to exchange for gems? Also, despite the daily challenges being random, some are too easy. This gets boring after 20+ days. The rewards for said challenges should also reflect on the difficulty: the more difficult the challenge, the higher the award should be.

bubbub1685 about Temple Run 2, v1.38