On fencing on the cheap, have you thought about posts and field fencing. We've got the metal T posts and a couple rolls of it around the garden right now to keep the chickens/dogs/rabbits out. We remove it in the winter, but it can be made more permanent and attractive. Goes up fast and will keep dogs out/in. If you want to make it permanent and pretty it up, plant box shrubs or vining type plants at the base. Once it all grows up and around it's quite nice looking. You don't even see the wire fencing.
If you use the metal T posts, you could do as much as you can afford now and then just move around to expand the area as you can afford more.
Our whole back yard is fenced off, kinda..... the house is on one side, the horse barn and coop on the other and the two sides are closed off - but the fence is low, 4ft. The chickens found their way over the fence etc...(I think the guinea's were first) and every day I'd see them pacing on the other side, I'd have to run out to let them back in.. every day more than once.
Finally, I lifted one corner on one side of the house, its right against the house and there is a cinder block to hold it just wide enough that the chickens can squeeze
through. on the other side we had a kinda gate, and I left the bottom of the gate open, they squeeze
through that as well.
So now they free-range all over, they LOVE the front yard, there are a few black walnut tree's and apparently there are lots of bugs under those.
Anyhoo - we'd have to fence the entire place - right now there is barbed wire all the way round the outside, I don't let my horse get near barbed wire, so their (horse and goat) pasture is fenced with field fencing - we have to use those big wood posts, the sandy soil doesn't hold those t-posts very well, not well enough for a horse with an itchy tush! 8-o
I also actually cut a hole into the horse pasture, just big enough for chickens and the ducks - they're in charge of spreading horse poop! 8-o and eating bugs in there.
Out of all my pets and animals, the chickens are by far the hardest workers, and then they give us eggs as well - there is no better pet on the planet!