As we were training in the months before the Camino, I evaluated many combinations of socks and liners. I ended up wearing medium weight merino wool socks (both Smartwool and Powersox brands), plus some ladies ankle-high nylons that for liners. I tried polypropylene and silk liners, but settled on the nylon because the were extremely lightweight, wicked as well as polypro or silk, worked well to isolate friction between my feet and my boots,
and they were free -- my wife had a whole box of them in her dresser drawer. However, I should add that my wife wore lightweight, ankle high WigWam synthetic socks without liners. We both applied a liberal coat of Gold Bond "Friction Defense" --
http://goldbond.com/friction-defense.html -- on our feet every morning before we started walking. Neither of us experienced any blisters for our entire 6 weeks on the Camino Francés.
This next bit of advice has nothing to do with socks, but it does pertain to feet, so I feel it's relevant to any discussion of socks, boots, and foot care. It concerns tendonitis and plantar fasciitis. If you have even a hint of these conditions, have your feet evaluated before you leave and get a pair of orthodic inserts to support your arches. This can be done by a professional or by the self-serviced machines that can be found at many stores that sell high-end running and hiking shoes, and even at most Walmarts. Once you start developing symptoms of these conditions, the only real solution is rest: getting off and staying off your feet -- not a practical solution if you're well into the Camino. I started feeling symptoms of plantar fasciitis around Leon, and being too stubborn (or stupid), I failed to address the issue and limped, at times hobbled) the last 300 km into Santiago in level 8 or 9 pain. It still bothers me at times, six months after completing the Camino.
Buen Camino,
Jim