I began thinking about how magic would effect a culture around my second sub, Magic: How it destroys conventional (medieval) siege. I continued to think about it in The PottyPortal. I probably had it in the back of my mind for far loner than that, but that is an unimportant detail.
Magic, by its very nature, would change how mankind developed, as far back as the Cro-Magnons and the Neanderthals (who, by the by, had bigger brains than us). Depending in the system, it would either be "wild" magic, and simply exist as something you could tap into, or be like math, and you need to figure out theorems and postulates and laws and such. The former would probably exist when we were all hunter-gatherers (there are hunter-gatherers out there today), the latter after a society chose to farm. Either way, societies development would have a completely new technological branch to explore- magic, which would be next to engineering, biology, astrology, etc.
How would this effect societies development? Would we even have a medieval era, which it seems most FRPGs are set in? Frankly, such an idea would require lots of thought, and a fair bit of research. So I am now focusing on one aspect of culture: the commoner.
Commoners should have magic. Oh, not a Ring of Super Blowing-Things-Up-Ness, but simple magic. Everday magic. Depending on the system, a mage could make lots of money if they made a potion that could hurry plant growth for farmers, or a rod that cleans the clothing item it touches. And so, this is a call out for those magic items. As inthe wise words of caesar193: "If I take over a country, I want the farmer's to get the latest in farming technology. Why? So that my troops are well-fed as they slaughter the next guy."
Additional Ideas (2)
Wand of Stump Removal
A plain wooden wand with a gnarled head, much like an old tree root, the wand of stump removal will briefly animate a tree stump to uncoil it's roots and drag itself out of the ground. This only works on stumps that are still alive, and not dead half rotten things, and the animation only lasts for a few minutes.
It's pretty simple and probably stupid. I assume others have easily thought of this. But if we're talking about peasants and magic I think that indestructable tools would be almost a must have. The hoe that never breaks no matter how many fields you sow, the hammer that can forge as long as it has someone to use it. And conisdering most set-ups say that magically enchanted weapons are auto-indestructable to standard means(i.e. rust, wear and tear) indestructability doesn't seem like it'd be so hard to put on a tool.