If you just want to learn to grind and aren't worried about whether or not you get a "knife" then go get about 100 of the big paint stirrers and grind blades with a 120 AO belt. With cleaning the AO belt should last you through that batch of stirrers. One big thing people forget when learning to grind this way, pretend it's steel!!!! Don't go into it with a "it's cheap wood for practice" attitude, practice like it's damasteel or something.
If you want to learn to grind and hope that you get a knife out of it then use simple steels, if you luck out and get a knife then you can heat treat it and move on to the next steps. Depending on the size of the 316 you probably can trade out for materials with someone.