Task List/hatch lv6
Some Eggs contain Gems when hatching them. Maybe you have noticed, that you seem to get them more frequently than at the beginning? The chance of getting a Gem when an Egg hatches gets bigger with each hatched Egg, and reaches 100% after 1,000 Eggs. So this is what you're aiming for!
Gems are a necessary resource to construct Gemwish Badges in the Wishforge, so having lots of them makes hatching more Eggs even easier. You could focus on one type for the time being to hatch the Eggs faster.