BMF had around 100 informants.
Craig Petites Enterprise had around half a dozen.
G.Ds had 263 informants during Operation Headache in 1995.

But the groups with the least amount that I know of is:

Black Souls, Not too much information on this street organization and a handful of cases on them. Not too many informants from them. Ratio wise could be on par with Genovese Family.

Mickey Cobras, Somewhat to my knowledge.

Black Guerrilla Family in California, Barely any new info on their activities on the street, no major cases, no documentaries on them, few articles on members interview, same old repeated info on net, secretive as can be.

Baltimore branch had somewhere around a handful of informants (the ones that haven't been killed) and more to come in the future.