Items have a wide variety of uses and valuable ones are often produced daily by LESPs and Nightmare Soul Puppets.
Many basic, but still useful, items can be purchased in various Item Shops dotted across Niflheim.
Click the icon near an item to favorite it and have it appear at the start of your item list during battle. Just click it again to deactivate this behavior.
Within the filter menu you can limit what entries will be shown within the various camp style menus. For example, if you type in "Bloody Gummies" and hit "enter", you will only see Bloody Gummies.