Sockwells are the best, in my experience. Veen wearing them at nearly at all times while awake for the past 5 years. Much better and more breathable than the purely synthetic compression socks. The sizing depends on shoe size.

Here are 2 examples of pairs with firm compression (20-30mmHg), which is what helps me most at work:

Sockwell Women's New Leaf Firm Graduated Compression Sock https://www.amazon.com/dp/B079C5K7CF/ref=cm_sw_r_awdo_navT_g_PN81BCXHSTPP3823BSC6?psc=1

Sockwell Women's Twister Firm Graduated Compression Sock https://www.amazon.com/dp/B01E5G7N0Y/ref=cm_sw_r_awdo_navT_g_AGND39X24JFM736W9BNK

If you order, make sure to use the sizing chart to determine which size you need.

edited to add link