Which part of your family are you focusing on?
My wife does genealogical research and she always finds it odd that people generally follow the male line when in reality you can only ever be sure of the female side of you lineage.
The way the DNA tests work, you have to test a male in the family. If a female is tested it only shows the mothers side of the family. My family history is well documented. Except my Moms, moms side. We think that my Great Grandfather was Jewish, and left Poland due to that. But he never would talk about it. When he came to the US he didn't speak English, so they gave him a new name (Joe Private, doesn't sound made up or anything
). There is also issues with my dads, moms side. It is said that her great grandmother was 100% Cherokee. During the trail of tears a lot of native americans changed their family names to more traditional names to avoid losing their land. We can't find anything beyond her, as her name was changed to Black. My moms dad, and dads dads family trees are pretty cut and dry. My Moms side were on the Mayflower, and one of my ancestors is regarded as the first child born to the pilgrims once they arrived.
https://en.wikipedia.org/wiki/Peregrine_WhiteMy dads side is a mixture of Danes and French. My Great Grandfather was born in Copenhagen, His wife was born in Idaho to English parents.