Here's an idea for gems!
IRL, rubies and sapphires are rarer than diamonds, they're just not as expensive because of the debeers monopoly. Anyways, I was thinking that, instead of having different gems worth different amounts and have different rarities, all the gems should have the same rarity (diamond-level rarity), but be worth different amounts to different gods.
For example, Zille might give 200 favor points from Sapphires, but only 150 for Diamonds and 100 for Rubies, while Mab might give 200 favor for amber, but only giving 100 for Sapphires and 50 for diamonds. This adds a new level to the game, encouraging people to trade gems they find. Plus, as it is now, level 4 mining makes it too easy to get tons of gems. It's much more fun finding a super-rare gem after a week's worth of mining than a bunch of common gems every day.