The best way to train prayer would to be either buying dragon bones or better from other players. However, if you have time and you want to save some money, you can buy some regular bones from Bob. They're only 4 coins each.
Bones and their experience
Buried, Altar or Weekend, Altar + Weekend
Regular Bones - 500, 1000, 2000
Big Bones - 1500, 3000, 6000
Dagganoth Bones - 12500, 25000, 50000
Dragon Bones - 7200, 14400, 28800
Ourg Bones - 18000, 36000, 72000
Best things to do while training prayer:
If you want to get the most experience out of your bones, use them on the regular altar. It doubles your experience of each bone. Also, if you use bones on weekends, you also get double experience. You can use bones on altars on weekends, so that'll be 4 times the amount of experience you'll usually get if you would bury them.
Thanks for reading!
Also, I'd like to thank Stacy, Nate, and Galio for collecting the bones for the Experience Chart
Made by Evan