In my case, it's not about DNA, it's about members of a landsmanschaft of which my family was a member. (Tiferes Achim Anshei Dinaburg, if it matters.)

I am using the "Friends and Neighbors" approach in the hope that as I grow this interconnected network of mini-family trees, I will find that some of them turn out to be cousins. I started by putting in everyone buried in one of the community's burial society plots, or mentioned in newspaper listings about TAAD, and so on. And I keep growing and growing those small trees and sometimes succeed in stitching them together.

I also have a tree where I'm trying to connect all known instances of the Werdesheim family name; that's now grown to 9 respectable full-sized subtrees and a few dozen scattered records that we can't yet connect, so it's the same kind of approach.