Blessings require a bit of gold and a fixed amount of materials. More blessings can be unlocked by collecting more Anna’s Mementos after reaching certain thresholds (5, 10, 25, and 50). There’s no specified materials needed (only quality) so this is a good way to enjoy the benefits of blessings while also getting rid of surplus materials. Better blessings will require silver or gold quality materials.
After collecting at least 50 mementos and upgrading the Temple to maximum, you can take advantage of the Rare-Materials Blessing, which significantly increases the drop rate of rare materials. With this active, you’ll be able to farm the rare silver materials necessary for better crests.