Now it's time to buy some $15 socks and $6 sock liners. Backpacking's expensive, isn't it?? This is why you buy the gear over a long period of time--whenever the sales come up, or you happen to have some extra cash.
Socks are important when you're going to be hiking all day. You want to make sure that your socks will wick away moisture from your foot when it sweats, but keep your foot warm when it's cold. You want socks that fit well--the heel of the sock needs to be on your heel, and the toe on your toe. You don't want the sock to bunch up at all--this will cause blisters. You also don't want seams to be too bulky. That end of the toe seam that bothers you a little bit when you wear tennis shoes?? Put that inside a boot and hike 20 miles and you'll have a nice big blister going. If your socks are too big, they will slide around and bunch up, giving you blisters. If your socks are too small, they will press on the end of your toes and the heel will bunch under your foot--giving you blisters. Blisters on your feet aren't good when you're walking many miles a day.
Vin and Gwen both have REI silk sock liners. Yes, we realize that we may get laughed at for have silk instead of poly pro or some other "more acceptable" material. But the fact of the matter is that silk is comfy, wicks away moisture, and keeps feet warm. These socks fit well, without sliding around, and keep our feet dry.
For outer socks, Vin and Gwen wear Smartwool hiking socks. These are the gold standard in hiking socks, in our opinion. Smartwool is an amazing material that will keep you warm even when wet, but is not the least bit itchy. Smartwool's hiking socks are made to fit well and not slide around, plus they have a little extra padding where it might be needed. Long story short, they are well worth the approximately $13/pair.
Be smart in buying and taking care of your socks on the trail. We carry three pairs of socks each--one is only for sleeping in, so we always have clean feet in our sleeping bag at night. The other two pairs we alternate between days so that we aren't wearing the same pair of socks two days in a row. This lets the socks dry and air out before you wear them all day again. When it's time to wash your socks, turn them inside out so that the part closest to your foot really gets clean.