In KeeperRL the amount of resources you have is limited: trees don't grow back, all ores are shown. Through the use of alchemy there is an exception with gold being used to turn into other materials.
Left to right: Gold, wood, iron, adamantium, stone, mana
You get gold by mining gold veins.
You need to store gold pieces in a treasure chest.
The alternative but surefire way of getting gold is by luring attackers into your keep and taking the ore from the bloody corpses, as they very often carry their purse with them. A defensive keep strategy will easily score a big gold count.
You get wood by chopping down trees or bushes.
The amount of wood planks per tile is more from trees than from bushes.
You get iron by mining ore veins.
The amount of iron ore per tile is randomized somewhat.
You get adamantium by mining ore veins.
Adamantium is used to build special dummies and finer, sharper, better weapons and armour than iron. Naturally occurring veins are guarded by golems that will wreck an unsuspecting keeper.
You get stone by mining granite veins.
You harvest mana by destroying an entire tribe
In free-play mode, you can get mana from studying in the library, if this option is turned on during the game setup.