It depends on many things, like how easy it is to gather and how much it is needed. A simple way to get an indication is to check what others charge for the items.
If you sell out your stock very fast you could probably increase the price. And if you dont sell anything the price could be too high. Some items are hard to sell because there is little need for them.
If you are trying to only profit from Foot Fall, then you are going to struggle with your ability to buy things to then resell. Since you are just starting out, your ability to buy large quantities of items is going to be heavily limited.
As far as prices go, I can tell you the current market average price for the items you have listed, but prices are subject to change drastically in the coming days when the next patch is due to launch.
Rock can sell for around 2-4c each, but not very often unless someone is starting a large build. Everyone ends up with massive amounts of it passively just from mining.
Fossil Extract is no long an item in the game with the next patch. It has been renamed and it’s price will very due to the requirement of spark to craft it now. Was: 5-8c
Bone is another item that sometimes sells, but is better used to just make glue and sell that.
Glue: 25-35c. This price will slightly increase as the next patch doubles the amount of items required to craft it. Was 1 each of both Bone and Sap, now 2 each.
Soft un-compacted Coal: 15-30c. This price fluctuates drastically depending on supply and demand. It’s price will probably remain the same or stabilize around the 10-15c area due to the increase in drops.
These are sell prices only, not anything resembling what you should buy at. They are also the average fair market value based off of the larger, more established and reasonable shops. My advice would be to sell only for your first few weeks, farming everything yourself. Once you have a few 100k coin then you can set up buy baskets and begin to buy things as needed. Never stop farming though. It helps to keep your costs down and maintain your low prices for established customers.