At the very least, string welded wire for fence and cover the pen top with wire for their nights. If they're free range, your day predators will be hawks and foxes, possibly coyotes and owls
on overcast mornings. Nights are when possums, raccoons, skunks & bobcats are active. Never put scraps out when they won't be eaten way before dark, build pen close to house and have on
some sort of floodlight aimed toward the pen. My chicken pen shares a fence line with my doberman and I think the proximity discourages the predators. My dog is a good chicken dog...she's never
messed with them, even when they've accidentally come into "her" yard. Snakes are will be active real soon (I'm in SE Texas). That's when the mothballs go around the nesting boxes and
I always try to collect the eggs several times a day, definitely before dark. I haven't lost a chicken in more than in 30 years to a predator (I've raised them here and in Calif for almost 40 yrs).
Good Luck and you're going to love having chickens!