First, this isn't my "healing" gear. It's not terribly different, I use the Price of Progress, and Gustwalker staff and PVP/spirit shoulders, so I have a lot more spirit than shows up on the armory, but I logged out after dailies.
I leveled and played as disc, and was happy, but as soon as I went into my first heroic, I have having major issues keeping both the group and the tank alive. POH was healing for like 20K, POM would hit a melee or 2 then bounce to me and sit there, and nothing I was doing was enough to save the DPSers from themselves.
I healed at 70 as a (different) priest, as holy and was pretty successful, and through Wrath as a resto druid and had a lot of fun, so I thought I'm just more suited to reactive healing and switched to Holy.
Holy was way better, no more mana problems, casting COH on cooldown with a few POHs+ the HOT was enough for all but the worst DPSers, but now I was having trouble keeping tanks alive. Gheal took too much mana, but heal wasn't enough to keep up with large incoming damage, using Chakra+Renew+COH was enough most of the time, but it required my full-tme attention on the tank.
So, I swapped to FDCL, since I was spamming Heal anyway, having the utility to throw instant, mana free heals that hit quite hard on any member I needed to was extremely useful for me. It also had the benefit of proccing serendipity, so I could cast POH or Gheal faster.
Now, my mana is doing fine and my throughput is much improved, but I feel like I'm doing it "wrong." I still have lots of trouble in AOE situations where everyone is taking lots of damage (Like Xin) or time when the tanks take big spike damage and I don't have and FDCL procs ready. I also know this strat won't fly in a raid.
So, any advice for a newbie priest, trying to keep people alive, sometimes despite their best efforts.