For the world's greatest roleplaying game. Dungeons and Dragons.
To brew a potion, oil, incense, elixir, salve, ointment, candle, philter, perfume, ritual, or poison, a recipe is often required for success.
The approach to brewing can be from Intelligence (Arcana or Nature), or Wisdom (Insight or Medicine).
Having proficiency in one or more of these skills plus tools grant advantage to the brewing DC. Tools that can be used are Alchemist's and Brewer's Supplies.
It takes on average 8 hours to brew a potion, oil, incense, elixir, salve, ointment, candle, philter, perfume, or essence unless stated in the recipe.
Cost for basic materials, workspace and crafting supplies range from 5d6 x 10 gp and most likely requires a special component(s).
A crafter needs a formula for a magic item to create or the process becomes mostly research that may result in many failures and costly experiments. The formula is like a recipe for brewing potions and such, but it is more intricate and involves incorporating the Thread of the Weave and various exotic ingredients. Each formula lists the needed materials, spells, mystical incantations, and somatic gestures required to make it.
The slightest mistake or variation can result in loss time, money, and or precious ingredients not to mention the potential of destroying the item and anything near it should things go horrifically wrong.
Crafting a magic item relies on Intelligence (Arcana) unless stated in the formula that a different ability may be used.