It is widely accepted that the pre World War II Gibson Mastertone banjos set the standard for how a bluegrass banjo should sound as popularized by Earl Scruggs when he joined Bill Monroe and The Bluegrass Boys in late 1945. Don Reno was with Bill shortly after Earl split and his sound was comparable to Earl's from a banjo tonal quality perspective, though there were some differences in their styles. These banjos were flatheads and used a 20 hole bronze tone ring. Many have tried to duplicate these tone rings.....Steve Huber, Mark Taylor, Jim Burlile, Bill Sullivan, and Jim Blaylock among others. Jens Kruger worked with European bell manufacturers to develop a new bronze tone ring for Deering, which was named the Tenbrooks model. For a great history of the really famous 5-string flathead banjos, those of Scruggs, Reno, Snuffy Jenkins, JD Crowe, Sonny Osborne and others, get a copy of Jim Mill's new book, "Gibson Mastertone Flathead 5-String Banjos Of The 1930's and 1940's".
If your budget can handle a bronze tone ring, that's what I would go for. If not, I'd try aluminum. My circa 1980 Alvarez starter banjo has a 20-hole aluminum tonering and sounds very good for a starter banjo.