Depending on where you live and wind loads, unistrut is a good choice, or unirack. I currently use unirack, but I am adding 20 more panels to my array and will be using just pressure treated wood. Currently I have my unirack attached to the top of 4x4 pt buried in the ground 3', with the 90 degree angles brackets lag bolted to the top after cutting to approx 24 degrees. As I add, I am going to use pt 2x4's attached to the 4x4's and screw direct. As my panels really don't have to follow the sun (yet) as I won't be using to full capacity it will work fine. I am totally off grid and have had no problems with the 4x4 system thus far. You can always change it later as money comes available. Also, check with local roofers, as when they replace a roof they usually do not reinstall panels, they suggest to homeowner to purchase new. Some good deals out there.
