The basic idea is, as long as you have 84+ max AP, you'll go infinite.
Use half-pot on Gem Quest, earn your 6k+ Gems, and you can spend that 6k+ on Gems Gacha and get one half-pot back. So infinite value. Or well, effectively, you're trading real-life time for gaining ingame resources...
Do notice that the maths haven't been confirmed, but it should be around there. So whenever those 30-minute Gem Quests pop-up, you can spend as many half-pots you want and you'll eventually make back all the half-pots you spent from the Gems Gacha - plus a crapload of free shit.Whoa whoa whoa, that is NOT the same thing. Yes, they use the same icon and the same mobs, but they're NOT the same thing!
Gem Quests - the things that appear for 30m at a time - give you a guaranteed 6k Gems per run, usually a bit more. Sunday Quests give you anything between 1k and 6k. I'd rather call Sunday Quests "exp cave" than Gem Quests. You will NOT reach infinite value with Sunday Quests ever.