Alright. So envision you're a trader on the stock market.
Only, you're not buying stock in companies, you're buying and selling magical stones, their values changed by the shifting of unpredictable planets and stars. Because astronomers are crackpots.
And owning certain stones gives you certain perks... only the perks aren't always bonuses, especially depending on the positions of the stars.
Stock Ticker: The TCG: Calvinball style.
New stones enter the trading pool as new traders arrive from exotic lands. And they may leave to other trading pools; players joining all join the initial pool (a big metropolitan area, like Ethshar of the Spices (if you've read those books)), but may "leave" for other lands, where there are other traders. They can't trade with players or NPCs outside of their pool, but there are always at least 4 other traders... if there are less, the pool is disbanded, and all the traders go to other pools.
NPC traders come and go, and sometimes "disappear" over seas, or wandering the wilds... only to meet up with enough other NPC traders to form a new pool, or to return bearing rare stones. Or objects of even greater rarity and worth.
The currency of the land, besides glowing rocks, is copper coins. The richest of the rich may have some silver, and seeing a gold piece is a once in a lifetime event. However, the stones seem to be able to draw coins from unknown space... and your pockets always seem to get lighter when the stars are in someone else's favor.
You do not do any wizardry, that is the providence of someone born to do wizardry. Each wizard, though, is very much tied to these stones; upon the casting of a wizards' first spell, several ordinary rocks for an unknown distance suddenly turn into the valuable stones that traders crave so much... It's quite possible that possession of enough stones tied to a specific wizard could cause something special... or perhaps not. And maybe it's not the stars that affect a stone's auras and powers.... but it is known that wizards do gain their power from the stars.......
Many mysteries surround the stones. And the rate at which they trade hands keeps anyone from truly figuring them out. Including why handing one over causes coins to disappear from one trader's pockets and appear in the other's coin purse without either laying a hand on a coin. Or why wizards will do almost anything to collect the stones tied to themselves. Or why they are always inedible. Or why they don't lose power when a wizard tied to them dies. Actually, that last one is pretty obvious.