>>532751479
>read/skip story until Atelier unlocks
>clear T1-T5 once to unlock the material stages
>grind material stages in rotation to get mats to unlock everything in the Atelier
>no need to return to T5, mat stages yield the same event currency as T5 and can all drop Isla as well

Ryza works exactly the same if you need to revisit that one.
It's worth noting that the Yumia dorm themes are unlocked through creating them one by one in the bland "Base" synthesis. Once an area is completed, it's possible to auto-place the full set in the dorm.