A straight upgrade to turn your Longspear into a +1 Longspear will help, in the long run you can then upgrade it further into a +1 Corrosive or Spell-Storing Longspear for extra damage.
Since you're a reach cleric, nothing wrong with stacking Enlarge person on top of a reach weapon and pushing for a 10-15' threat zone. If they do manage to close, 5ft step back and wait for those attacks of opportunity to come in as they close again.
Other than that, scrolls are a good investment and if you don't have one already, a Wand of Cure Light Wounds saves you having to worry about converting your healing spells too often.
One final item which can help out, is either extra-dimensional storage such as a Hewards Handy Haversack, or a set of Muleback cords if you can spare the cloak slot. The former lets you carry a *lot* of spare scrolls, potions and alchemical items to help give you options in combat which aren't "stab them with the spear", the latter just lets you carry a lot more stuff than you'd otherwise be able to lift.
