Some of us have fav dragons we got from season lines, but sometimes we don’t complete the line. Then, as we level up, we have to sadly shelve those dragons because we can’t level them further without evol stones.
Not all of us can afford the sigil chests when they are available to complete the season lines.
The game remembers bought dragons, like Ember, and we can buy value packs at our leisure with evol stones for them.
My suggestion is to have the game either remember those dragons we don’t have evol stones for, or value packs with a “magic orb” or some such, which can be any evol stone we want it to be.