I would wear moisture wicking attire. Don’t spend a lot, just go to any place like Target or Old Navy, etc. You can get some exercise clothes there. Don’t wear shorts like in the picture, because I’ve heard that bees & such get caught up in the leg opening.....ouch. Something like tight running shorts, or even bike shorts would work.
Given the reclined angle, you might want a hat with a brim under your helmet. There’s a product called “Da Brim” that is a hat brim that goes over your helmet. Made for recumbent riders. Wear sun glasses, preferably polarized. Sun screen.