I'm like you: I survive with two pairs of socks. However, I use them differently.
Once every 24-48 hours I wash one pair, hang it on my pack to dry while I walk, and wear the other pair. At the end of the day, I put on the freshly washed pair. If it's not dry yet, then I just leave on the pair I have been hiking with, or, more likely, I sleep barefoot.
In fact, sleeping barefoot is one of the best things you can do for your feet during a long hike. They breathe and dry out faster than if you're wearing socks. Of course, if it's snowing outside, you'll probably wear socks.
Since you've proven you can survive with just two pairs, I would stick with that, unless you're heading to a very rainy or cold place, in which case you should bring the third pair.
Finally, get the thinest socks you can tolerate so they dry fast and let your feet breathe.