Some of the spells were neutered but clerics can still do well. The main problem you are going to face is that nearly all of them have short durations while your team mates don't really need much time to spend buffing. This means that for the "big fight" you will keep up with them, if you buff, but for the rest of them you will still lag behind.
Don't let that discourage you. You are a full spell caster, and if you kept up with them without using your spells then it would be extremely broken.
Spells:
Bless, Divine Favor, Magic Weapon, Aid, Bull's Strength, Magic Vestment, Protection from X, Prayer.
Those are all available at your level and they all buff. (I didn't check to see if any given spell overlaps with any other given spell though).
-S
Since your Chaotic... would add to list: Entropic Shield.
Might also check out: Shield of Faith.
Another trick is to Hamper your foes. After all causing your target to take -4 AC is just like buffing yourself with +4 to attack.
Spells like: Bane, Doom, Hold Person (been nerffed badly), Bestow Curse, or Blindness/deaf,
Great opening spell: Sound Burst: 1d8 points of damage in a 10 foot diameter burst, and if they fail their Fort save, they get Stunned for 1 round. Now getting stunned for 1 round might not sound all that great, but A stunned creature drops everything held, can not take actions, takes a -2 penalty to AC, and loses its Dexterity bonus to AC(if any).
What I can't figure out is what these "self-buffs" are (I've heard people say PFS cut down on cleric buffs from 3.5?), and what exactly "melee fighters or summoners" really means, esp. to a cleric. Has anyone played a cleric and knows what spells might really aid in actually dealing damage?
The neutering of clerics and druids melee combat ability was delibrate. Clerics no longer have buffs that make them a better fighter than the fighter and druids larger forms no longer let them become 8 limbed dealers of grapply death.
What feats do you have so far? Is it too late to abandon ship on the melee cleric?
If you want to deal damage your best bet is spells.
Level 1: command to flee, and have them draw attacks of opportunity, or fall and make them prone
2nd: Sound burst is nice. The damage is meh, but stunning multiple people can shut down a small group of opponents, essentially giving the entire party an extra action.
Hold person is nasty, just delay your action until just before the fighter or rogues turn , paralyze them, and let the fighter or rogue coup de grace them.
3rd: blindness is NASTY. Its basically save or die, since almost nothing that's blind is going to live very long. It lasts until cured.
Holy smite is nice vs evil creatures, and is functionally a fireball that leaves your party alone (HOPEFULLY) against undead.
4th: Poison
Look over the summoned monsters. They're really good once you get to summon monoster 3 or 4, but you have to know what they are to pick the good ones for the situation you're in. Your rogue will love you.
If you insist on meleeing
1) get a big honking 2 handed weapon. You aren't going to hurt anything whacking something with one hand, no specialization, and slower attacks. If you can't blow the feat on a 2 handed sword or don't have something from your deities favorite weapon, use a morning star in 2 hands.
2) A longspear is a simple weapon with good damage that takes 2 hands to use. You can poke people as they come at you, and if you can't back up resort to touch spells. The attacks of opportunity will give you a few extra attacks.
Spells
Its important not to spend too much time buffing yourself. each round you spend makes you more effective.. but also costs a round you're standing in the back doing nothing.
Cause wounds is always a possibility, especially against heavily armored opponents. Its not always the most damage you can do, but its almost a sure thing, given how hard it is to increase touch ac.
1st: divine favor, shield of faith
2nd: aid,bulls strength (if you don't have a str booster), silence: put it on your fighter as he runs at the casters.
3rd: Magic vestment.
4th: magic weapon, greater : Divine power.
Don't forget enlarge person, which you get as a 1st level domain spell. And you can always fill it in higher level domain slots if you want it more often.
It won't increase your attack bonus (net change +0) but it will increase your damage due to increased strength (+2) and weapon size. A 1d8 morningstar will grow to due 2d6 damage if you are enlarged.
It also increases your reach by 5 ft, so that you would threaten all squares within 10ft of you.
Use your weapon two handed unless you really need the AC from a shield. Morningstar is a solid choice, as it does two types of damage. Longspear is a little better, as it has a x3 critical multiplier and reach. But being limited to simple weapons means theres no better option for you than a base 1d8 weapon.
Do you have Power Attack? If not grab that as soon as you can. This will let you keep the damage up.
At 8th level you can cast Greater Magic Weapon to give your weapon a +2 enhancement bonus to attack and damage (although it won't stack with the +1 to attack with a masterwork weapon). This will increase by one every four levels after 8 (+3 at 12th, +4 at 16th, +5 at 20th).
Divine Luck will give you at level 6 give you a +2 to attack and damage, although it only lasts a minute.
Bulls strength increases your Str by 4 for a minute per level, so that equals a +2 to hit and a +3 to damage (if weilding a weapon in two hands). Although it won't stack with a belt that increases your strength.
The trick with the cleric at higher levels is to be able to get buffed as quickly as possible. Quicken spell helps with this a lot, as you can get a low level buff and a high level buff off in the same round. (e.g. quickened divine favor in a 5th lvl slot). Extend spell can also help, as you can keep some of your buffs up longer so that they might be active in multiple encounters.
You'll also need to be judicious with your buffs, as you don't want to spend three or more rounds buffing up while a fight is going on, only to find that your party has killed everything while you were getting ready. So consider the situation and figure what will be best to use. A single divine favor might be all you need for a particular fight. Other, tougher fights might call for a full battery of buffs.
So I'd say grab Power Attack, Extend Spell, and Quicken spell, in that order, to help get your damage up more. If you really want a tougher weapon, you can always consider Martial Weapon Proficiency and grab a greataxe or a greatsword, although I'd probably grab Heavy Armor Proficiency before that. (I'm assuming you're not a half-orc, dwarf, or elf? They get racial proficiencies with some better weapons for free.)
Read through the cleric spell descriptions so you can see what spells will help you out. They are there, you just need to learn what to use and when to use them.