An undiscussed topic about Maker

You don't upgrade plates, you just use them for certain items. Plates don't add stats, but they're part of the recipes to forge items. For example, you need 4 Adamantium plates to forge most level 100 weapons.

Jewels and crystals actually have different grades and act as 100% scrolls for the "extra slots" you get when you forge an item.

I prefer to think of it as add-on options upon creation instead. I'm also told you can't use more than one type of jewel per equipment, like say two diamonds, regardless of grade.