Here are a few options to increase your chances to land a spell on enemies:
Spell Focus: Choose a school of magic and apply +1 to the DC of
all spells of that school.
Greater Spell Focus: The previously
chosen school is now +2 DC.
Spell Perfection (at 15th level): Choose one spell to master and double
the bonus from Spell Focus. Won`t be available anytime soon, but should be listed here for reference.
Heighten Spell (Metamagic): This
will allow you to cast spells using higher spell slots, which
automatically increase their save DC.
Focused Spell (Metamagic):
Increase the spell level by one to increase the DC by 2 on a single
target of a spell that affects multiple targets.
Yes, you should consider ways to debuff your enemies that allow no save, or spells that lower their saves:
Cause Fear: One creature up to 5 HD becomes frightened if they fail their save (which also applies -2 to checks from shaken), or if they pass, they become shaken for one round.
Prayer: No save, debuff their attack rolls, damage rolls, saves and skill checks while buffing your party at the same time.
Sacred Space: Sancities an area to increase all good spells DC by 2, or against evil outsiders, which also debuffs their attack, damage and saving throws by 1.
Or effects that apply the Shaken condition (-2 to saves):
Intimidation: Intimidating a foe is the easiest way to make an enemy shaken, and can be done even by a fighter or rogue in your group, but preferably, should be someone that invested a few feats on it.
Doom: Will save or shaken.
- Bestow Curse: Will save or -6 to an ability (wisdom) or -4 to attack rools, saves, and ability and skill checks.
Or effects that apply the Sickened Condition (also -2 to saves):
- Ray of Sickening: Fortitude save or become sickened for 1 minute per level.
- Dread Bolt (if you are evil): Causes damage against good targets and apply sickened if they fail a will save.
- Unholy Blight (also for evil casters): The opposite of Holy Smite, will cause good creatures to become sickened if they fail a will save.
Be aware that creatures immune to mind-affecting effects will be immune to fear effects.
There are options from other classes that are available either as multiclass or by other party members that you could benefit from, but are also readily available (at first level):
Evil Eye (witch): Applies -2 to either attack rolls, skills or saves, even if they pass the save, the effect lasts for one round.
Misfortune (witch again): Target that fails their will save will have to roll twice and take the best result on any ability check, attack roll, saving throw or skill check for one round.
Spell Bane (inquisitors): While your bane ability is affecting a creature type, all your spells DC increase by 2 against that creature type.
If we knew what was your deity and cleric domains (or even the composition of your group, afterall it's a team), we could also suggest some domain abilities that could help, but i believe you got it after all these ideas.