There are runestone items that drop sometimes that are kinda neat but they are "ancient" and only have a few uses. It would be neat if Dwarven artisans could craft new runestones for things like Bull's Strength, similar to ioun stones but for other buffs that people use regularly for another option. My current thought on how they'd work mechanically and material requirements is perhaps make them one or two per day uses of whichever spell but make them cost prohibitive to prevent people from just buying a full set right out the gate on every character. So maybe something like the following:
Item Crafted
Runestone of Barak (Strength)
Bull's Strength 3/day
Crafting Cost
1 Marble
1 Raw Star Ruby
1 Mithril Dust
Requires Dwarf
Requires Cleric/Wizard
This would give value to raw rare gems and would be a dwarf specific item that fits with lore. It'd also provide the opportunity for mundane characters to weigh the cost of potions/scrolls against buying a runestone to use instead for specific buffs, and it would provide a use for gemstones that will help pull more gemstones out of gem bags. Alternatively these could be charge based but less expensive to make as the above idea may need to be balanced against how common or uncommon things are so that they aren't impossible to get but also aren't worthlessly common.
Also an option would be to make them more expensive but have them function like a staff sequencer situation where a spell can be applied to them so players could have a runestone of mage armor for example or a runestone of death ward. Or have a sequencer stone that requires a bunch of different rare gemstones to make that is far more expensive to craft that does this. The basic buffs that mundanes use and that can generally be bought from merchant NPCs though would be nice as a more late character option for a source of animal spells, mage armor, shield, barkskin and such. It'd help make the weight of gear lighter for non strength characters and cut down on inventory clutter for everyone not having stacks of potions/scrolls constantly depleting and being refilled