I don't have a preferred seller yet. I wasn't that satisfied with the first two. The first one, I overpaid. But I made a rookie mistake: NEVER buy a lot from a stock photo. Buy or bid on the actual coins in the photos. It wasn't an auction site and it was from a seller with a website who specializes in uncleaned ancients.
The second was a cheap lot from
ebay so I wasn't expecting much. The coins in this lot are still uncleaned, so I don't feel confident in recommending them that. However, I did buy them from an experienced seller on
ebay. Just search uncleaned Roman lots, you will probably see similar photos and figure out the seller. I also bid on a lot from a seller from London. I really just examine the coins and then bid I'm happy with about 2-2.50 per coin. If you see some silvers (and some add them) maybe bid a bit more.
Resources I used about cleaning:
I like this one the best - easy to read and follow:
http://www.kersh.com/coin_cleaning.phphttps://www.crustyromans.com/cleaning/http://www.metaldetectingworld.com/...n_coin.shtmlGood Luck!