Valkyria Revolution

Sabancci & Co. is accessed by speaking with Basil in his Factory. You will be spending your found ragnite here to infuse into everyone's weapons, giving passive bonuses to their stats. Make sure to remember and equip higher level ragnite on your soldiers before infusing it all so they have strong spells, but once they have some good ones the rest you'll use to upgrade the weapons. The level of the ragnite will increase the amount of points given to the infused item, so make sure if a slot only needs 25 or so to upgrade, you give all your lowest level ragnite to it, then use your higher level ragnite on nodes that need a bigger amount to limit waste. Once a node is completely upgraded, you will get that bonus stat as a passive and the node will have a blue highlight around it.

I would suggest maxing out Godot as soon as you can, or his sister Miranda depending on where you are in the story. Without spoiling anything, you'll only have access to one of them at a time during the story and they share the same weapon, though after the story is over, they'll each have their own. If you max the shared weapon before the story finishes, it will simply be duplicated to the other person and stay maxed out. If you don't max it first, it will duplicate however it is sitting and you'll need to finish maxing both weapons, costing you more materials and time.

One thing that can speed this up is by crafting a pouch using three Reinforced Pelts. Each one gives the item 7-9% of extra drop rate, so it'll be 21-27% in all. The pelts are sold by the Traveling Merchant who will show up in the Promenade from time to time, or you can earn them via Battle Reports. Keep an eye out for him during the story, as I'm not sure when exactly he starts selling the Reinforced Pelts. I bought them post-game when I started my grind.

Use the same method as for "Golden Flower Commemoration Medal" to grind this out.