I like the 5.11 pants. Just good pants, great for the range. Like how the mag stashes in the back pocket for playing speed games. I went to wearing the underarmor shirts years ago when they first showed up in the army --I was a diehard cotton guy until I tried those, now I don't wear cotton shirts anymore.
I always wear my boonie, boots, ear and eye pro. But I sort of dress like this all the time, I'm always ready to go to the range. Lucky for me, it is just down the street and open from 7am to 10pm 365 days.
I don't wear shorts (unless it is god awful hot) or open shoes. Don't go shooting without the eye and ear pro either, seen what happens when you leave that behind.
In the army, they used to make those guys wear the helmets, the armor, all the junk. Said to "train the way we fight". Nonsense. Shooting at a range at pop up targets isn't training, it is target shooting. So at our SDM school, we abandoned the helmet, armor, and other stupid army range rules. Our uniform became the boonie, black shirts with skull and crosshairs, BDU bottoms, and black or brown boots (the only real issue gear we wore were the pants --and we got away with it too-- mostly because the army doesn't spend much time at ranges and that is where we were all day long!) I still sort of dress this way out of comfort, just don't wear the BDU's or the range instructor shirt.