Jungle Spores

The glowing green orbs grow on jungle grass down at cavern depth, and you have to break the orb itself. They are bright enough to spot from a distance in a dark tunnel, so sweeping the lower jungle horizontally finds them faster than digging around. Once picked, the orb is gone for good and cannot be replanted, so harvest as you explore rather than saving spots for later.

Swing a Sickle instead of a pickaxe and you pick up Hay on the same swing. If you are already down there, there is no reason not to.

Selling raw spores is close to throwing them away. Turning a full stack into Jungle Hats first multiplies what the same material is worth by a large factor, which makes an afternoon in the jungle a genuine early money source. After Skeletron the better use of the same stack is Void Vaults, which are worth more again and are also the only reason most players farm spores in bulk at all.