This is a major wip but right now I'm making this guide so that I, and other users know which items to keep for crafting applicators and what items they can sell.

Eventually my plan is to separate each category into Feathers, Gems, etc and show each craftable item and its recipe.

Eye Apps:
-Dry Palm Leaf
-Locust Wing
-Herb: Dream Root
-Shoebill Feather
-Nightjar Feather
-Beetle: Sternotomis strandi [Cyan]
-Ostrich Feather
-Gem: Carnelian
-Gem: Celestite
-Gem: Fire Opal
-Gem: Jasper
-Gem: Peridot
-Gem: Tanzanite
-Gem: Sparkling Opal
-Gem: Rough Opal
-Gem: Labradorite
-Gem: Amethyst
-Gem: Cat's Eye
-Gem: Dioptase
-Gem: Garnet
-Gem: Star Ruby
-Shining Drongo Feather

Mane Apps:
-Bloodbath
-Hyena Lands
-Fuchsia Flower
-Four Leaf Clover
-Flamingo Feather
-Ostrich Feather
-Locust Wing
-Shining Drongo Feather
-Common Raven [1]
-Gem: Bloodstone
-Gem: Howlite
-Gem: Labradorite
-Gem: Moonstone
-Gem: Nuummite
-Gem: Rhodonite
-Gem: Amethyst
-Gem: Rough Ruby
-Gem: Rough Opal
-Gem: Moss Agate
-Gem: Meteorite
-Gem: Kunzite
Gem: Hematite
-Invocation
-Possession
-Shiny Rock [Red]
-50x Snake Skin - Dark
-Underbrush
-Herb: Ubhubhubhu

Marking Apps:
-Space Rock
-Comet Shard
-Underbrush
-Prismatic Scale
-Ionized Plankton
-Cheetah Skull
-Locust Wing
-Rainbow Stones
-Murex Shells
-Shiny Rock [Teal]
-Gem: Amethyst
-Gem: Carnelian
-Gem: Fire Opal
-Gem: Nuummite
-Fuchsia Flower
-Large Leaves
-African Cucumber
-Herb: Honey Bush
-Herb: Uvuma-Omhlope
-Herb: Umganu
-Herb: Dream Root
-Herb: Uzara
-Herb: Uqume
-Herb: Iboga Root
-Herb: Ubhubhubhu
-Shiny Rock [Red]
-Small Rock
-Antelope Hoof
-Stripped Cacti
-Kingfisher Feather
-Phantom Quartz

Base Apps:
-Ammonite Fossil
-Ancient Fossil
-Cracked Fossil
-Crumbled Fossil
-Gem: Hematite
-Gem: Kunzite
-Gem: Meteorite
-Gem: Moss Agate
-Gem: Rhodonite
-Gem: Rough Ruby
-Natural Glass
-Locust Wing
-Murex Shells
-Rainbow Stones
-Fuchsia Flower
-Four Leaf Clover
-Aloe Leaf
-Flamingo Feather
-Ostrich Feather
-Shiny Rock [Red]
-Shoebill Feather
-Herb: Dream Root
-Herb: Nut Grass
-Herb: Buchu
Herb: Uvuma-Omhlope
-Herb: Umganu
-Herb: Imphepho
-Herb: Marula Fruit
-Human Bones
-Underbrush
-Tail Tuft Hair
-Shiny Stones
-Lion's Tooth
-Lion's Claw
-Lion Skull
-African Cucumber
-Stripped Cacti
-Beetle: Lycus trabeatus [Yellow]
-Beetle: Smaragdesthes africana [Yellow]
-Proagoderus rangifer [Green]
-Gem: Bloodstone
-Gem: Howlite
-Gem: Labradorite
-Gem: Moonstone
-Gem: Nuummite
-Gem: Rough Opal
-Antelope Hoof
-Kingfisher Feather
-Porcupine Quill
-Kudu Horn

And that's it! If all you're interested in crafting is base apps like me, then these are all the items that you'll need to keep. everything else can be sold!