An excellent source of Prayer earnings is Dragon Killing. Their bones grants significant amount of experience and don't require an extremely high level of RuneScape gold skills. To take out Blue Dragons below the Taverley (in Taverley Dungeon) you do not require a lot of resources to do so since they can be killed in a safe place. If you decide to do this, be sure that you should do it using Magic as they're not immune to this particular style of combat. Use large eggs, rocks and columns to get Dragon stuck and complete them with your spells.
Alternately, you could kill Green Dragons north of the Graveyard in the Wilderness. Make sure you bring an Anti-Dragon Shield, food and equipment. Don't take anything too precious to avoid losing your money on Player Killers. Also, you could consider farming on Void Knight Equipment as you're not likely to lose it dying with it on low Wilderness. It's an ideal option to use for Dragon Killing and a safe one to use in this zone.
All bones that you collect should be sacrificed on the Chaos Altar, but it is not a safe method, so don't take anything other than the bones you'd like to sacrifice. This is among more Player Active zones on Runescape, and it is located at the 38th level of buy 2007 runescape gold Wilderness.