Socks
The best system with socks is to wear a very thin liner pair next to the skin, with a medium (not too thick) layer on top; this way the two socks tend to rub one against the other, rather than against your foot. If you can find Bridgedale “1000 Mile” double sided anti blister liner socks, so much the better.
The thick socks can be any reasonably strong trekking socks, but don’t get anything thicker than roughly midweight, as the combination with the liner will otherwise be too thick.