You will need at least two pairs of good walking socks, one pair to wear and one pair spare.
Some people advocate taking three pairs in case feet get wet on consecutive days and there is no drying room access.
We found that despite their robust construction, after a week of walking the sole of the sock became significant compressed so we'd advise that you change to a fresh pair of socks half way through your hike.
Our socks were 'CoolMax' socks, and like all good walking socks, had no seams to cause rubbing and were designed to wick perspiration away from the skin.
For added comfort and protection we also wore sock liners.