Ditto on DH's advise!
I wear a half size street shoe which forces me to either buy a wading shoe a 1/2 size or 1-1/2 sizes larger than my street shoe to get a proper fit.
(No Virginia, most wading shoes I've tried DO NOT fit if you buy them in your street shoe size!)
Since every wading shoe I've ever owned gets TOO tight if I just buy a 1/2 size larger, I go with the 1-1/2 size larger option. Because of that I have been using an extra pair of insoles with NO ill effects for many years. I use an insole called
Body Cushion made in Allentown, PA that seem to last forever. I have a few pairs that are almost 20 years old and still going strong. They have fabric bonded to the insole material that reduces or prevents the slippage that DoubleHaul mentioned.
I also wear heavy wool socks in the winter
and when I wet wade, which I started to do on Friday

. When I wet wade, I make up for the loss of the neoprene bootie in my waders by wearing a pair of neoprene
Guard Socks made by Simms.
Those wading shoes may seem a tad big to you now, but if you fish in the winter, you'll LOVE the extra room!
Good luck!