There are various things you can do daily to rack up the gems and items. Let’s start with the achievements page.
The Story tab has different achievements for different things. Everyday you can receive items for completing
Completing 1, 3, and 5 Mirrors battles respectively
Clearing 1, 3, 5, 10, and 15 Story battles
Upgrading Memoria in any way
There’s also long term achievements you can receive, such as increasing the rarity of 5 magical girls, unlocking a magical girl’s full magia gauge, unlocking doppels, ranking up, and so on. There’s even a gacha ticket for every ten days that you log in.
You can get the Mirrors achievements whether you win or lose, but you have to win the Story battles for it to be considered cleared.
Labyrinth Quests can only be cleared once per weekday, so if you clear all the missions for Monday’s set of battles, there will be another set to clear on Tuesday.
But any battles you cleared on Monday will remain cleared from here on out. You can only clear the battles of each day once ever.
You're allowed a single ten pull of the Normal gacha for free once per day.
The free pull from the Normal gacha won't carry over, so be sure to use it each day.