If thrift stores don't work well for you, I've had great experience using C9 gear from Target. It's all UnderArmor-like gear, but like 25% of the price. The boxer-briefs (9") are still my go-to underwear when I'm doing anything outdoors and avoiding cotton. They've held up incredibly well, they seem to repel smells fairly well (by polyester standards, anyway) even after eating Taco Bell, they very much help protect from chafing. They make good socks, too, but they might end up being a little more expensive than some "dress socks" that will most likely be easily acquired at a thrift store. What I like about athletic socks over dress socks, though (as long as the socks aren't cotton, you'll be ok), is that athletic socks tend to be contoured L/R. Since feet are L/R anyway, the angle of the toes as well as support for the arch makes a great deal of difference, in my experience anyway.
A good rule of thumb is that when you do splurge, splurge on how well you can sleep, and splurge on your feet. Spending an extra $1 per pair of socks is a worthwhile splurge if you ask me