In order to get another prayer book, you need to have your first prayer book complete (i.e. with all four pages) before Jossik will let you buy another one (costing 5,000gp each). An alternative to buying the god pages, you can instead receive them as a reward from doing treasure trail clues. All the various god pages can be a possible reward from any level clue scroll (1, 2 or 3).
Simply pray at another altar. You will be asked if you either want to change prayer lists, or just want to recharge your prayer level. For a guide on how to increase your prayer level: http://gameolosophy.com/games/online/runescape/how-to-train-prayer-in-runescape
Roughly about 300,000.
It depends on how high your prayer level is.
Lots of people have different opinions on what best to wear in Runescape, but IMHO I would say that wearing the saradomin robes set with a blue h ween mask and a prayer cape.
There is something called a "Protect from Magic" Prayer. But you need a prayer level of 37.
2Mill
A pure
Bandits in the Bandit Camp in the Desert are great to train on as long as you have 43+ prayer and prayer potions.
Runescape money is used for several things throughout the game. One would need Runescape money for things such as skills, magic, firemaking and cooking, crafting and prayer.
I've left a link in the "Related Links" below
You can "scatter" it for Prayer Experience or you could just plain sell it.
If you bury bones, you will level up prayer. Increasing your prayer skill will also increase your combat level.