You'll be spending many hours on your feet each day as you walk and navigate the paths of your Camino de Santiago. So, choosing great socks is important. They provide support and cushion for your feet and, depending on how long you're going to walk, they need to hold up to daily hand washing and line drying.
Most packing lists include packing two pair of socks, but they don't usually tell you what kind of socks to pack. There are lots of choices, of course, but my favorite, by far, are Smartwool Socks. The heavier, hiking crew socks. They've got a reinforced heel and toe, and they held up to 7 weeks of hiking. Actually, I'm still using them.
Also, if you damage your feet and end up with blisters or sores, the liners will add a soft layer of comfort, too.
While the more expensive Smartwool liners are nice, after damaging my feet (which was gross) I found that buying ankle footie socks at the small shops (usually 3-6 pair for a few Euros), I could wear them once and discard them.