Use what you have
Let's take garden beds.
When we first started homesteading, and needed raised garden beds, the inclination was to buy the lumber .. even though we had many acres of trees. The inclination was to buy mulch, when .. we had acres of it, in the form of "whatever you rake up from the forest floor." The inclination was .. still .. to look to modern conveniences.
After doing this homesteading thing for awhile, such thoughts never happen. It's quite the opposite in fact. "We need to buy..." turns into "What can we get from the forest to satisfy the need." Although MY 4x4 lumber is round, has to be debarked and is often actually 5x5 .. it functions just the same .. doesn't require a trip the the hardware store and costs zero.
In conclusion, the best material for making garden beds is ROCK. Rock garden beds will last a hundred (thousand?) years, cost nothing and as an added bonus, the act of building them makes you stronger. The rock also absorbs heat during the day and releases it as it cools, thus allowing your carrots to snuggle together nicely at night. That's my theory, anyways .. and I'm goin' with it.
The other day, hair wilded by the winds .. I stood in the breeze, with my warmest of friends, the sun. I quaffed an ale, one that I'd made. As it dribbled down my unkept beard, flowed onto my shirt, I felt not the slightest consternation; not the slightest self consciousness; not the slightest worry. In that moment, I was a king; a great rebel king. I wanted nothing more other than to share it with someone, yet, my court was my shadow; good company still.