It seems when the whole "#menswear revolution" went off years ago, hand in hand with the slim flat front pants, contrasting buttonholes, and loud bowties, wearing crazy socks was one of the first ways guys started trying to express themselves and their newfound style. Like most things related to that phenomenon, it was probably just a little too much for too many men that weren't ready to make that type of statement (yours truly included in that group).
That being said, socks are still one of my favorite accessories, and can add a kind of cherry on top to a great outfit you could say is similar to the contribution from a well-matched pocket square. Tokyo-based brand Anonymous Ism makes some of the best for casual wear I've found.
Alongside CHUP, another Japanese-based sock brand, Anonymous Ism is well-known for combining high quality materials and construction with interesting colors, patterns and designs that largely manage to avoid the whole "LOOK AT MY F*CKING SOCKS" vibe you can sometimes get from less-finessed design. The pairs I have are holding up beautifully. The problem is that they're usually on the more expensive side for most, unless you find paying $25-30 for a pair of socks to be not a big deal. Me, I'm personally trying to decide right now if adding chicken to my noodle dish for lunch is worth the extra $2.
Club Monaco currently has a decent selection of Anonymous Ism socks on sale for as low as $9 (plus shipping) right now, though I've been sitting on them hoping they'll have an extra discount code this week. $9 is probably the lowest price I've seen them for on their own as it is, with normal sale prices usually being in the mid teens at end of seasons sales. If you're interested in upping your casual sock game, this is already as low a price as you'll likely see all year. If an extra discount code comes up, I'd consider it an insta-buy.
Also keep your eye on J. Crew's stock, who recently had CHUPs on sale for $12 (+ extra code discounts). Those sold out quickly.