V-coins and ma-shops are reputable and you won’t easily come across fakes there. Just stay away from Ebay and the like. Also, if you go for the affordable types (common denari or late roman bronzes) these are almost never faked since it’s not worth the effort. They cost like 5 bucks for decent pieces, maybe just a bit more if you want a nicer specimen.

Ancient coins (2000-1700 years old) are surprisingly common and can be had very cheaply unless you want a specifically rare or perfect one.

I went through most of my life believing that anything older than say 200 years was automatically a museum piece or equivalent. But most museums of ancient history who display ancient coins have multitudes of the displayed coins sitting in storage. The Romans alone minted BILLIONS of coins over the span of the Republic and the Empire (that’s over 1000 years of history!) and if even 1% of them survive today, that’s still many, many dozens of millions.