How far back is too far?

[Me cousin Jack]

I've been looking into my family tree recently. My maternal grandfather was a Douglas, but I haven't been able to trace his lineage past his father. A little further up my tree (still on my mother's side, father's side was all English), I come across McCulley, 3 generations back. Again, I haven't been able to trace this lineage to determine which of 3 different clans they were a sept of. Going further back, 6 generations, I get to McConnell, which I do have information goes back to the 6th generation descendant of the fourth chief of Clan Donald South. So I'm 15 generations from the fourth Donald chief (6 from a McConnell daughter), 3 generations from a McCulley daughter, and one generation from a Douglas daughter.

So how far back is too far? Should I stick with Douglas, being the nearest, even though they're the branch I have the least information about?

With regard to what? Choosing a kilt? Were it me, I’d wear either one.