I gave a coworker permission to shoot me if I ever show up to work in lycra. It's in writing.
My favorites are merino wool t-shirts I got at a deep discount, though at ~$35 they're still kinda pricy. A long sleeve over a short sleeve with a windbreaker worked quite well today. I also have some $10 synthetic wicking t-shirts which work almost as well, but they get stinky faster, and I don't know that they would have kept me warm on a day like today, when it was still breezy and cool (in the 50s). On the lower half, I wear regular pants if it's cool, and cargo shorts if it's warm.
In this transitional weather, I don't know what to wear. In the last couple of weeks, figuring it was still cold, I wore regular cotton shirts, managed to sweat anyway, and then nearly froze to death. I'll try not to do that again.