Awesome, for a cloistered cleric who only gets to choose two resistances which ones would you recommend graystone?
Fire and Cold are solid picks. Poison and bludgeoning are good ones too. Really depends on what you think you'll run into.
For instance, fire/cold is a common weakness/resistance/immunity and attack form [often the same creature] which can be a double-edged sword [you take less damage but so do they from your breath].
Poison too if fairly common but more often you don't find creatures doing poison damage and being resistant/immune to it so it boils down to what you are fighting/encountering: if you're fighting undead, your breath isn't going to do anything for instance or if you're going to encounter a lot of traps and creatures with poison it could be great. Remember, your breath will target Fort so it's going to work better on a different set of creatures, which could hurt/help: might be bad if you use both breaths all the time or good if you only throw one when it's convenient.
Bludgeoning is a nice protection to weapon/unarmed attack and has a nice balance against weaknesses/resistances/immunities. It also has that nice unique burst Breath of the Dragon, which can be a huge boon in trying to position it to hurt foes and not other PC's.
Now if I was going in blind... I'd go Sea [Bludgeoning/Dragon Disciple] and Brass [Fire/Dragonscaled]. Fire and physical attacks are so common you're likely to run into it somewhere in any game and I find lines better for aiming/targeting than cones [cones are better to hit more creatures but often PC's too]. That and spitting out an exploding water ball is cool. ;)