Very difficult. There seems to be no real rhyme or reason to the combos. Even though you can practice on day 0 with 3 ingredients, even writing those down isn't much help because day 1 adds 3 more ingredients which exponentially increases the combinations, and you immediately get customers asking for the new items those combos can make, and you have no way of knowing how to make them aside from trial and error while the customers inevitably give up and leave because you're not psychic.