As far as metal pipe goes:
3/4" EMT conduit weighs about 4.6 lbs per 10ft.
1/2" EMT conduit weighs about 3 lbs per 10ft.
A fun "Buy it for life" product I recommend is MakerPipe, which allows all sorts of connections. Not quite tinkertoys, but it's fun enough and highly modular. When I'm in a place in my life to raise chickens, my plan is to design a few pens with this material.
Check out
https://www.makerpipe.com for products and
https://connect.makerpipe.com/homesteading for homestead ideas with MakerPipe. There are plenty of chicken pen builds for inspiration.