My alt -an i560 Discipline Priest with Legendary cloak -is running on the free version of Oracle via Tyrael, both BuddyStore editions.
I have *no idea* of what to do with Discipline beyond the basic concept of the class and rotation, CDs etc. The Oracle CR performs quite well and generally (25N and 10N) I can outperform healers with higher iLvl and experience. I have found that, of course, manual intervention is required with healing; many encounters require you to do stuff *before* some mechanic hits... which is what I find frustrating. I also find that every CR's UI looks horrible and feels like some 90's college VBScript project when compared to the multitude of options that TuanHa's CR suite affords. I find myself manually having to pre-empt PW:Barrier and Spirit Shell, though as soon as I do click Spirit Shell the CR automatically applies Prayer of Healing though not on necessarily the correct person/group.
That said, as others have recommended, Oracle runs quite well despite the clunky basic interface.
With Mana, until you are geared, go with Spirit -I believe AskMrRobot will advise the same -as you may OOM with lower gear. IIRC my healer sucked until I progressed beyond LFR.