You don't need armour to train prayer, it's only burying bones.
If you want to train combat with prayer bonuses though, the best f2p stuff to wear is monk robes, a holy symbol, an explorers ring, and a mace (corrupt dragon is the best, but it only lasts 30 minutes, so use rune if you can).
There is no "best" armor in runescape, but armor such as the "nex" armor (Torva, Virtus, & Pernx) are some of the more elite types. Nex armor is dropped by the monster Nex in the gwd.
Best for what? It varies a lot, depending on whether you want to maximize your defense bonus, your prayer bonus (to make prayer points last longer), and - in the case of a defense bonus - what type of attack you want to defend from.
Granite armor is the best armor to wear with 51 defence members.
Just like everything else in runescape, saradomin is the number 1 best armor in runescape since it is the most expensive. 4-5 mil
Full Rune.
The best ( but most expensive ) has to be armadyl.
Proselyte armour.
The best armor to wear in Runescape I would say is Bandos, mainly because a nice combination on Strength bonuses with Defense.
a nobermom
The best armor for free-players is Rune, God armor is the same the same thing, just painted with the colors of a God. For members, the best armor is Dragon, also the most expensive.
dragon arrows.like armor and weapons,dragon is the best besides special items.
The best spot on Runescape Train Attack is in between lumby and vorok, go to beefy bill, or in al kirid fight guards with friends.