I had bad luck with some gaiters.
These hurt my legs. Altra gaiters wore out so fast and since I don’t wear Altras (with gaiter traps) the Velcro would not stick or even glue on. That was frustrating.
Rain gaiters worked well for me but they are heavy.
I’m trying these next https://www.simblissity.net/levagaiter.shtml as I have a pair.
My wife wore Altras but is getting displeased with how short their life span is. Soles separated after a hundred miles on her most recent pair.
I need gaiters when hiking in shorts. With pants the pants hang down and keep the detritus out. I’ve been really pleased with that.
PCT vs Appalachian Trail difference. The PCT has a lot of gray sand. It is really ash from the fires. Hundreds of miles of it. It will slide right through the mesh uppers of shoes that aren’t waterproof and permeate your socks.
Since my feet don’t sweat much, I like to hike with GTX (waterproof) trail runners. Which is good since for my shoe size (between 40.5 and 41.5 in wide, depending on the brand) often GTX versions are the only ones available/in stock.
The difference in how my socks end the day between the two different types of shoes really got my attention.
I bring this up since gaiters don’t protect against the problem.