I suggest talking to your party/DM and explain that you're feeling kind of irrelevant and sidelined because of how powerful the other characters seem in comparison to you.
Having read some other answers and your responses to them, it looks like you're playing with some allies that are rather optimized (Sacred Geometry, for example, is absurd) while you seem to be not as optimized. It also seems like you're looking for a single feat/item/whatever that you can pick up to instantly boost your save DCs' by a significant margin to catch you up with the combat strength of your party members. Unfortunately, no such option exists, otherwise they would eclipse all other options, and with your other party members being spellcasters as well, they would also have specc'd into it. To increase your DCs' your options are basically going to be Spell Focus and something that boosts your WIS score.
My suggestions are thus:
Forget the save DCs for the most part. You're playing a Cleric, which is one of the best buffing classes in the game, and one of the top 5 classes in the game. Prep spells like Prayer, Bless, Angelic Aspect, Ice Armor, and especially Magic Weapon and Greater Magic Weapon and similar spells. Blessing of Fervor, deserves special mention. The divine version of Haste, it grants a stronger buff than Haste, but only to a single option each round. It also allows any character affected by it to apply one of four select Metamagic feats to a spell they cast each turn for free, and your Bard and Magus will love you for it. Don't focus on being the center of attention, focus on enabling your allies.
Or perhaps focus on summoning. The Summon Monster spell line is very good. It has the benefits of improving your teams action economy, providing an extra target (or targets at higher levels) for your opponents to split their damage into, and it allows you to make attacks while ignoring your own poor offensive stats, plus they also will benefit from your buff spells that you'll likely be throwing around anyways!
If you decide to delve into the art of summoning, there are a handful of feats you'll want to get you started, namely Spell Focus (Conjuration), which, while unhelpful to your character overall, is a prerequisite for the much more important feat Augment Summon which will buff the STR and CON score of any creature you summon. Since you can already cast level 3 spells, and are shortly going to gain access to level 4 spells, you can start summoning real outsiders, like elementals and imps and things. My personal recommendation is to drop down an earth elemental during the first round of combat followed by some sort of buff spell like Bless.