Depends on what a person is going to do with the Ring necks.
If just pets, I'd build the run at least 200 sq. ft. plus their weather structure (for a pair or trio).
(as mentioned, bigger is always better)
It also depends on where it is placed, soil type etc.
Best way to keep any Pheasant species , is to plan an aviary well in advance.
Get the building all done, as well as the run.
Before the wire/netting goes on (shouldn't use netting on the sides, they can/will get their legs or feet tangled up and hang to die) the landscaping should be done. Shape for drainage. Get the trees, bushes etc planted and all singes of dirt work allowed to grow in.
Don't kill any weeds. First thing they'll go for are clover, dandelions etc.
If you are in a dry area, water the grass like you would your lawn. The trees etc will need watering anyway.
Hens of nearly all species will need places to hide from the males. Plant with this in mind.
Make sure to check for toxic plants, trees and bushes.
I read here about using Junipers. The berries on some types are toxic. I still use them, but make sure all berries are picked off at all times.
Cedars that are not meant to grow tall work, and take trimming well. I use Brandon Cedars in all my aviaries.
I have posted pictures on my aviaries.....but they get bumped back too fast due to the volume of people here....I'll see if I can find it. It may help you plan your aviary.
Found it:
https://www.backyardchickens.com/forum/viewtopic.php?id=278483
I have all the wire to finish this. But I'm having huge troubles finding hot dipped galvanized staples to attach the wire. (going to start searching B.C. today......) The EG (electro galvanized) staples, start rusting in the first week.