British crowns (.925 silver pre 1920 and .500 silver pre 1947). German states 5 marks, French 5 francs, Spain 5 pesetas- the list goes on and on. Availability would be the main issue in certain countries. If you want real budget, then most countries will have coins without silver. I mentioned the coins I listed as they are of a similar size to US dollars and guessed it was that size of coin you wanted. UK cupro nickel crowns are 10 a penny in the UK, maybe not so where you are.
I'm pretty new to this myself, but from what I've seen so far, Mercury Dimes and Wheat Pennies seem to also be popular among American collectors. Or pretty much any silver-containing coins, like the half-dollars and quarters prior to a certain date (1964 or around there). Check out reddit.com/r/coins to see what's in vogue.
Everyone is giving great advice. I assume you mean something similar to the size of a silver dollar? For American coins don't forget the Peace dollar. I have found more of those in better condition than Morgans at a better price.
