Crafting

Item School: The School of magic that a magical ingredient falls under, some may fall under multiple.
Item Categories: Categories that specify what the crafting ingredient can do within its school. Like schools, a single ingredient can have multiple categories.
Item Tiers: The power and quality of an ingredient.

Item tiers scale from tier 1 to tier 8, with each tier having larger maximums than the last. Utilizing higher tier materials at lower stats (range, damage, AOE, etc) leads to lower DC's, while moving closer to the tier maximums leads to higher DC's.
Remember, you can use multiple low tier components to get the effect a single high tier item would grant you, though this is always to a limited extent decided by your DM depending on the item.
The maximums for each Tier goes as follows:
(Tier 1) 1d6 damage, 15ft Range, 5ft AOE,