I have been thinking of the time/money factor vs. the ease of buying as well, Bsfman. And I definitely agree that it might just be worth it to buy instead. The biggest problem I think would be the kiln building, not the actually preparation of the clay.....I have no pottery experience, so it would all be experimental for me If nothing else, I will keep contemplating and experimenting with the goal of making my own grow media in the future!
Gravel may indeed have to do. I found a place in Dallas that sells expanded shale. Dallas is a good half of a day trip, but might be worth the drive. I will have to check into TXI, though. Another idea is to go to the plot of land that my family owns on the Blanco River and harvest some river stones (composition check is a must, but I have HCL!!). The river stones might be good middle ground between buying and making??
Other than the fact that I am trying to do my first system on a restricted budget, I am also concerned with environmental detriment in the way that some of the stone and clay is mined.