Ragg wool socks from the sporting good store don’t cut it and weirdo gaudy multicolored affairs are just silly and overdone.  Here's something that's extremely underrepresented by reenactors: U.S. Army Issue Socks.  Machine knit by contractors in industrial knitting mills by the millions, Army socks were usually made from drab colors wools, sometimes with white heels and toes, with little to no ribbing at the top.  They were also made from a much finer gauge yarn than what most reenactors are used to.