Entirely depends on how hard I’ll be training that day. Simple trigger control drills? A t-shirt and whatever pants I grab. BUT, if I intend to be rolling around then more appropriate and sturdier clothing is needed. Some of the newer 5.11 pants are absolutely brilliantly designed and have become some of my favorites. The new stretch materials are super comfortable in any condition/position. Several models also do not scream “tactical” which is nice for out-and-about wear, but still have a lot of great features like separate pockets for spare mags, knife etc. I should mention that I DESPISE collared shirts at the range. They are fine when I’m by myself but they seem to be a funnel for hot brass when shooting in a group.
Many folks forget that feet need good protection no matter what and Merrell footwear has not failed me in many years, though I also wear very sturdy Danner boots on occasion. Of course I have hot and cold weather options in clothing and footwear.