A lot depends on your location... wind, soil composition, slope, animals to be confined, etc. I probably wouldn’t go much farther than 15’ in any case. We’ve found that the t-posts out in the lumberyard (Menards) are less expensive and stronger than the ones on the shelf in the garden dept. They...
I use 2x4” 6’ tall welded wire fencing on my runs (woven wire is stronger) Turkeys will jump up and roost on it, but only where it’s tarped (makes it look solid). My chickens do not, but they’re all fairly large breeds. Smaller birds might jump out. I skirt the base with 1/2” hardwire cloth to...