Ink

The most common of the inks (ergo the name), common ink can craft the lowest level of spells. If a spell's lowest level is above common, it cannot be crafted with common ink. The same goes for all other inks.

Less common than common, it can craft slightly more powerful spells.

The rare ink should be able to be found regularly in magic treasure chests or by killing spellcasting mobs.

The best place for epic ink and all other high rarity inks is from magic treasure or killing spellcasting mobs.

The most rare ink, it will craft the most powerful spells. Keep in mind, some spells have multiple legendary levels, requiring use of the Arcane Anvil to obtain them.