Wearing Dress Shirt Without Undershirt?

You could get an undershirt with a V-neck so you could have the top buttons undone, either way it really depends on climate and fabric. Linens will be more resilient and less-sweat boosting, but full fabric shirts will trap in sweat and induce it further. I had a dress shirt that I got a good three years out of before the cuffs and underarms went off, I wore an undershirt while wearing it, so sometimes it's not even stoppable either way. 

I would recommend it, undershirts help to trap that sweat and dirt we sometimes have. I’m a sweater so I need a shirt, you don’t want to be the guy who has huge stains on the front and back your shirts.

I never wear an undershirt and never sweat through it, maybe slightly in the summer in armpits but being in an air conditioned office it's not really needed. Looks dumb too.

All of my colleagues and people I meet don't seem to wear one either, think it may be a US centric thing.

You should plan on getting new dress shirts every 2-3 years because of this.

I think an undershirt under a dress shirt looks tackey. But, occasionally I use one, in the winter months, or in more formal attire as I sweat and while i normally don't mind, I don't want it to show.