Typically just wear a pair of athletic shorts over my long underwear. Thinking of getting a pair of wader pants for this next season.

Any recommendations?

For the last 3 years I’ve hunted in uninsulated breathable waders and when the temps drop, I don’t hesitate or think twice about what to wear beneath them- Sitka Gradient wader pants. They are tapered in the leg, so they don’t bunch up. Under foot strap keeps them down all the way and makes it easy to get into and out of waders. Have pockets and an adjustable waist belt that stays in place and doesn’t catch on the inside of your waders if you wear a wader belt.
I’ve had them for three years now and they still look brand new even after all the abuse and weekly washings during hunting season.

During the warmer days, I wear the Wrangler moisture wicking elastic pants that are less than $15 at Wally World.

I use Columbia, pockets are nice for keys and wallet etc when in transit, and extremely warm body booted in them In Chesapeake

https://www.amazon.com/Columbia-Mens-PHG-Wader-Pant/dp/B005D6B1E0

Rogers by far is the best bang for the buck. I've seen them on sale for $29.99 during the summer.

https://www.rogerssportinggoods.com/rogers-toughman-tech-wader-pant-brown

If you want to spend the money, go Sitka. I like the Grinder Pants because I feel I can wear them on more occasion than just under waders, but the Gradient would probably be a better dedicated wader pant.

For $30, I might pick up a pair of the Rogers that Barney suggested. Those look great for a dedicated wader pant