So, today I was working with a free chest, and sold what minor items the vendor was buying and looked and what less-than-useful items he was selling. Then I scrolled down to consider what I could spend gems on…and then considered just buying some gold with the few gems I had. Oh, but not so fast…
But as you can see, unless I had 500 gems (I rarely have more than 250), you couldn’t buy coins with your gems. It’s generally a bad idea not to let users make low-end trade ins. Always keep the low-end option for players who are still working their way up.
Build a mechanism for players to sell the old, useless, common cards they will never, ever use again. You can buy them really cheap, but give the player something for them.
Give players more control over things they can buy in the store. As they progress, Rare cards should be more readily available, when they’re no longer using commons and tend to be using epic gear and higher.
When players aren’t able to have more control over their fate, they start to lose interest because of the RNG nature, and play less.
So, just my $0.02. You are the ones who have to make a living at this; but without players, there’s nothing to make a living from.