I just started putting a course together for training and due to limited $$ I had to get a bit creative. I have a hay wall, I raided the firewood pile for large unsplit logs and have used them to support the poles and I'm going to collect a few logs from a neighbour. My poles are a mix of pvc and wood but I must say I prefer my wood ones, they're a bit more solid and I cut a wedge out of the ends so it sits flat and doesn't roll. I only use these on low jumps and keep the pvc for higher ones.
I should be getting a bunch of old wooden pallets to pull apart as well, it's actually been a lot of fun to think outside the box this way and it certainly gets the horses thinking!