Firstly I would advocate for a rarety system with resources common resources could be collected just be the base tile type within your cities borders. I guess common resources would be things like food, timber, rock and possibly even weaker metals like bronze? Uncommon resources could be higher quality versions of the above plus some exotic resources like herbs/horses/iron that are used for research/units and rarer resources are the pinnacle of that type of resource like magic pool(research?), bears/griffins, mithril ect.
Well as I see it Elemental has the ability to have a resource used within our empire in 1 of 3 ways. All of which could be used at the same time, so the system I’d propose covers strategic (within the empires borders) as well as production of the resource (within a city border or in the tile of a city).
A. Within the Empire borders.
B. Within a city’s border (i.e area of control of that city)
C. Worded tile within a city.
The first way ( A ) could grant you the ability use that resource for product, research etc aka as it does in Civ4. But you get no bonus production for having the resource, just the ability to use it.
Having a resource within a city’s border ( B ) grants you production of that resource in your city, i.e. your people gather the resource and bring the resource back to that city. I would give a production value of 1 to each resource collected this way.
Lastly having a resource worked as a tile (i.e. with an improvement building) within your city gives you a large bonus to the amount of that resource that you can collect, since your population doesn’t have to travel to work the resource.
As an example of what I mean take a resource like Bears.
If you have 3 bear resources in your empire then you can build/train bear cavalry throughout your empire. Each resource will grant you say 1 bears in the warehouse of each city that controls (within borders) that resource. Further more if the resource is being worked as a tile in a city, say a ?stable? has been built on that resource that give it say +400% production for that resource.
So if 1 city has a bear resource within its borders it will produce 1 bear a turn. While another one of your cities is working the 2nd bear resource tile and has the last bear resource within its borders then it would be producing 6 bears a turn (1+1+4(400% production bonus for the worked tile).