Welcome aboard, Stephanie!
For pricing you just set one price per size. Each time that size sells regardless of the material that is what you earn.
When you look at other people's work you can click on the "show price details" under the price to see what the print markup is for that particular piece.
Generally, I'd say price higher than you think you should. People tend to under value their own work.
As for earnings, some people earn nothing in a year while others may earn $10,000 in a month.
For those that sell occasionally to daily, the views to sales ratio seems to be somewhere between 400 to 2,500 views per sale. Some people may have 100 views per sale while others may have 20,000 views per sale and some may never sell anything.
As with most things, "It depends".