I can safely sell earrings right?

[NDN Shadow]

The ones you get from the amusement park? Are there any other materials that aren't used for crafting?

[PepperoniSlammer]

Yup

[gadman85]

I've seen that the game tells you in the item's description if it is 100% safe to just sell the item. I've noticed other items that can be sold as well to an extent that aren't marked that way.

[uschgu]

You can safely sell any item, that says "can be exchanged for money". These items are not used for crafting.

Though you get one of the endings by eating the fish you get in an sidequest in the desert camp. Save first! ;)