Unfortunately, Silver grinding is pretty limited without DLC. Reasonably good Silver drops tend to be somewhat rare from pots; most of the time you're just getting one per drop. You can spend time in dungeons waiting for glowing enemies to spawn; they always drop Silver.
Post game, Thabes has much better Silver drops. If you make it to at least the 8th floor, I'd say you're guaranteed about 150 Silver per run? You could get a lot more though if lucky. There are also drops for wine and foreign spices, but those are rarer.
Basically, before post game, it's rough.