I am agreeing with Tormy. Perhaps elaborating a tad.
Basic resources, such as stone and wood, ought to be generally available is modest quantities. However, if you control a resource source for these basic items, you have a much higher supply in quantity, and perhaps quality. So you will always have some lumber from local trees, but if you have a nearby redwood forest and a sawmill, you have a lot more wood. You will always have some stone to work with, but having a quarry gives you much more. So even without the quarry you can build slowly, but large projects (such as a cathredral or walls) really need a quarry or they will take forever. Spending gold to purchase the resource from another player will mitigate that...if the other player and you agree on a price.
However, if you cannot agree on a trade with another player, I would prefer that you not be able to spend gold to buy the resource from some invisible market. If there are no quarries in your part of the world, one ought not be able to buy quarried stone regardless of your gold supplies.
Regarding more rare items, such as iron. As implied in earlier Frogposts, any city will generate a little bit of it even without a resource. If the soveriegn needs iron, the peasants can pull old nails from the junk woodpile and get a little bit. On the other hand, if you have an iron mine, you get a lot more. If you are going to equip an army, you better have an iron mine.
However, for the rare items...diamonds or mirthril ore or dragon scales to tip your arrows...those are not lying around. Find them or buy then, no automatic small availability like with iron or wood or stone.
Since we are considering a game with up to 32 players, we are in the fortunate position where we could use market forces to set prices, rather than artificially set the prices of different commodities. In other words, use supply and demand to set prices, like in the real world. To do this we need an active market in commodities and some sort of market or meeting place where things are regularly bought and sold.
Perhaps in games where the world has become developed and connected, there will be cities in central locations where players might often buy and offer for sale the special items they have created and found (as discussed in another thread). Using the same system that offers to sell special items, a player might also offer commodities they want to sell. Send your carts of excess wood, stone and iron to the market in Minas Tirith and offer it for sale at a price you want. If others don't buy it, lower the price until they do. If it sells quickly, set the price on the next load higher and get more for it. If you need stone for your walls, buy it in the city (though you may be financing the army which lays siege to your walls later!). If you control the city with these sales, institute a 5% tax on the market place and you're rich.
If the market town benefits all players, it may develop a tradition of a 'Peace Town' that is better left alone than attacked because if you attack it, you shut down your source of critical supplies. Or perhaps a greedy player wants to sieze the town to take over the market tax revenues or confisicate items for sale...so the other players form a commercial league to protect the trade zone. You can see that the diplomatic as well as economic possibilities.
Balancing the game's supply and demand can be tricky, but that that is an economics topic for another post.