There are a few ways to get Silver:
- Silver is collected in tax from your population. Build more and upgrade existing Housing to increase your population capacity and Silver income
- You can drag nobles to the Treasury in the Keep to boost this Silver tax, you can also ask others to send a Noble to your keep to Help boost the Treasury (and you can send someone to help boost theirs)
- You can send Nobles to Trade Posts (which you can find on the County Map) to trade your excess Food, Stone or Wood for Silver. Dungeons also sometimes contain small traces of silver
- You can loot it from other players by attacking their city or performing a 'Heist' in their Treasury
- Finally you can find silver in some of the store bundles