Are there any dumb terminals that, I don't know, stand above the rest? Like a make/model that would be ideal? Or any that should definitely be avoided?
DEC (Digital Equipment Corporation) terminals are generally considered the best serial, text-only terminals. IBM and Wyse brands are also very good in general, although with IBM you have to make sure it actually has RS-232 support (they made some that just interfaced with their 820 series of servers). I have a really nice, relatively modern Wyse (150, I think?) terminal with an extended PC-like keyboard (green screen) that I use a lot.
I'd recommend a terminal that was made in the late 1980s or early-mid 1990s for the best mix of features, price, and relatively compact size. I have a few DEC VT-125s (early 1980s era), and while they are really nice, they are also very bulky.