Once you’ve decided “I want to give them a scroll now” or “I think it’s time they deserve to get a spell staff”, how do you go about choosing which spells those are?
I assume different people have different ideas here, there isn’t one right answer. This is meant to be an open-ended discussion prompt.
I’ve got two methods for scrolls.
The first is “Don’t bother with anything they are capable of casting by themselves.” As in, I’ll only drop scrolls of a higher rank than their top slots. The flashier the spell, the better.
The second is “The player is actively seeking this out in-character,” in which case I’ll just drop a cache of 4-8 of the spell at the end of a mini-quest performed alongside whatever the current job is.
I’ve got one method for wands.
Is the spell something with a persistent effect? Then bam. There you go. I’ll never drop a wand that loses its utility as soon as you spend the actions, or worse, as you level up. Spells like fireball are a no-go, but spells like Shape Stone are great.
And as for staves, I’ve got two again.
One, does the staff have a good evergreen first level spell (or more) like Illusory Object or Heal? Then it’s going into the loot piles.
And two, is there a thematic link I can make to where the staff is found? That’s a going on the baddies’ fireplace mantle to sell their aesthetic.
I like to use the weird spells that players rarely take due to being less than optimal. That way they still get to use them situationally, without having to “waste” a slot.
The exception is when there’s a particular story reason for a certain type of item to crop up; for instance, a group of assassins hunting a powerful mage might have a lot of dispel and antimagic type things.