Gemming seems rather fine, except there isn;t much to gem yet
. Now that hand of purity is on 30 sec cooldown, I'd go with clemency pretty much every fight. You never know when you need that extra sacrifice, since purity won't really keep your tank alive during a crisis and don't think there are any bosses atm leaving tanks with heavy ticking dots. I always liked cooperating with the tanks with double sacrifice, it made it much easier for them to plan out their own cooldowns.
Also, light's hammer. If your raid isn't stacked on a fight you would rather go with holy prism.
Not rally sure about spirit/mastery gems for 60 stat bonus, could be a good idea or a bad idea but we don't have fixed stat weights and mastery got nerfed a little bit, so unless the bonus is a 120 stat I'd go with pure spirit gem(your mana regen is really low at the moment).