Holy pally pvp is insane, I have never died in a 1v1 yet, even against a Dk which went for 10 minutes of him self healing. I never divine plea and didn't drop below 50% mana.
You want to use holy shock as much as possible, flash of light is powerful but uses a lot of mana. Word of glory should be used whenever availible at 3 holy power as it doesn't cost any mana. You should be getting mastery from your gear so you put a bubble for a % of what you heal.
As for gems you want to stick to 20 int, 10 int 10 spirit and 10 int 10 haste for red, blue and yellow sockets respectively. Divine plea in combat whenever you aren't healing anything, marrowgar 10man heroic trinket is very nice alternative to a battlemaster's trinket for the mana use, but Purified lunar dust it easily BiS along with a medallion of the horde/alliance (even as human).
Forestgimp - Holy/Protection Paladin - Khaz'goroth US (Oceanic)
Sammiches - Assassination/Combat Rogue - Khaz'goroth US (Oceanic)
Drøød - Restoration/Balance Druid - Khaz'goroth US (Oceanic)
Assviolator - Arcane Mage - Khaz'goroth US (Oceanic)