Co-operator for random low-level summoners up to SL 45 and down to SL 5
Starting Class: Cleric
14 Attunement (base)
9 Endurance (base)
7 Vitality (base)
12 Strength (base)
12 Dexterity (shortbow for pulling)
7 Intelligence (base)
Rings: Clutch mandatory in respect of your damage source, Ring of Favor and Protection (+1, +2) very much recommended, Prisoner's Chain to compensate for otherwise low stats, Ring of the Sun's Firstborn if you like to cast miracles for damage, Darkmoon Ring if you like more miracle variety
Catalyst: 'Talisman' if you prefer Talisman's over chimes or otherwise Priest's Chime
With weapons you are restriced but the straight sword category is really strong. I suggest Broad Sword or Longsword, though the Mace is very handy as well if you like the playstyle.
I am not parrying myself so I prefer a Blessed Eagle Kite Shield +2.
Miracles aren't too impressive on the offensive side in my opinion (and the opinion of a lot of others). You can of course use Great Lightning Spear. Also Dorhy's Gnawing is an option.
You focus on healing, with Med Heal healing huge amounts of HP at that SL and with 1 FP bar you get 2 heals. Also self- and party-buffing with Sacred Oath. Tears of Denial if you are facing a boss where you consider it useful.
I prefer not to have to buff my weapons mid-fight so I go with lightning infusion as main damage source and a raw and blessed infusion for resistant enemies or respawning skeletons. Works of course also at this low level though your damage will shine with a raw weapon and Lightning or Darkmoon Blade.
Having a +2 fire and deep weapon also helps with resistent enemies.
The big wall for me on this low level character was the Dancer. Luckily you can use Dorhy's Gnawing on this build. Using the pillars to bait attacks after which you can safely attack also helped a lot.
This build is very nice to help out random people up to the Catacombs of Carthus. After that you will still get summoned, just expect it to take longer.