Co-operator for random low-level summoners up to SL 45 and down to SL 5
Starting Class: Pyromancer
11 Vigor (base)
10 Endurance (base)
8 Vitality (base)
12 Strength (base)
12 Dexterity (shortbow for pulling)
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, Witch's Ring if you focus on pyromancies over melee for damage, Darkmoon Ring if you like more spell variety
Catalyst: Pyromancer Flame for regular and dark Pyromancies, Caitha's Chime or Sunless Talisman for dark miracles, 'Talisman' for healing, White Hair Talisman if you are switch-lazy
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.
For spells you will use Great Chaos Fire Orb and Dark Fire Orb. You have also acess to the dark miracle Gnaw which might come in handy occasionally.
For healing I prefer Med Heal which still heals a reasonable amount of HP at these stats and with 1 FP bar you get 2 heals. You can also consider self-buffing with Deep protection and switch in 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 chaos and dark infusions 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 compared with a raw weapon and Carthus Flame Arc.
The big wall for me on this low level character was the Dancer. Dark Fire Orb did more damage but tended to miss more for me than Great Chaos Fire Orb. Just figure out what works best for you. 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.