Well, it depends really what your emphasis is going to be. You say you want to do more pvp than pve. If you're intending to do arenas you'll definitely want to go down as far as pain suppression in the disc tree. Its a real life saver in arenas in particular.
There are plenty of deep disc builds floating about for this type of thing in particular, you will however need to incorporate some more pve based talents into your build to deal with threat etc. since you mentioned running instances.
Any build that you come up with in order to do both of these things is going to compromise the other in some way, but there are things that you can sacrifice and still do either to a reasonable level.
Assuming you want to go deep disc I might go for something like this
http://www.worldofwarcraft.com/info/classes/priest/talents.html?tal=5052020130525002031051230350300300000000000000000000000000000000
This assumes you're going for a healing type build and not a smite spec of course.
This build incorporates some of the better pvp discipline talents in order to increase your survivability in pvp whilst maintaining some of the more important healing talents in the holy tree.
Having not tested a build like this myself I couldn't tell you exactly how well it would perform in either aspect of the game,at the end of the day its one of those things you're going to have to try out yourself a few times until you find a build that suits your style of play.