I leveled holy the whole way with my pally and I had the same problem with the lack of spell damage on plate Items at a lower level. What I did was to try to find any healing gear, and gear with int and get a nice, slow, high damage 2her. I would start off judging Seal of Crusader (for spell damage bonus), put up righteousness (which gets a boost from weapon damage and spell damage), and then holy shock, I would continue to auto attack for a bit until holy shock was up, do that, judge righteousness, and then Hammer of Wrath to finish off the target (if it was still alive).
That set up worked well for me, but was pretty mana intensive, luckily you're an alchemist so you make some potions to boost your mana pool if it is getting low.