Material option has 2 usages. You can defined a minecraft material, or you can defined an ID of an Item from a different plugin that will be used!
If you want to use a regular minecraft item, just use "material: STONE" for example
Usage: "material: itemsadder:namespace:id"
Usage: "material: oraxen:itemId"
Usage: "material: hdb:headId"
Usage: "material: mythicitem:itemId"
Usage: "material: aquatic:itemId"
"display-name" set the name of the Item.
"lore" is a description of your item.
"model-data" is an item NBT tag that is being used for Resource Packs
"amount" sets an amount of your item. (min. 1, max. 64)
"enchants" is a list of enchantments that will be applied to the item
"flags" is a list of item flags that will be applied to the item