Bountiful adds a Bounty Board to Minecraft that gives you random tasks to find items in exchange for rewards.

The board will automatically generate new tasks over time and the rarity will change as well. There’s also a time limit for each task that varies depending on what items you need to collect.

After you collect the necessary item(s) just right-click on the Bounty Board and it will automatically exchange those items for gold ingots and nuggets.

The rewards can be modified depending on if you want to be rewarded from other mods or different items from vanilla minecraft. However that requires editing the .JSON files in the config folder.

This mod does require an additional API found here.