The first time I played it, I got to level 15 or so. I think I started with a knight, and was using medium and big swords. Those tend to hit the walls more than the enemies, and heavy armor doesn't really work in this game (at least at low level).
After that, I started over as a sorcerer. I got to level 29 with that, and got a good idea of what I wanted to do: magic, with enough str and dex to equip the things I wanted. 16 dex, 16 str and 36 int. As much ranged as possible, and a sword and shield. Start by using spells, parry when they get close and use a fast sword with a powerful thrusting attack, preferably one that can do that while parrying. A spear does work as well, but those don't have a sweeping attack for groups (like the Blight Town flies, or simple undead).
I started a pyromancer (with masterkey) and got the spider shield and estoc, but I wasn't satisfied with that and started farming the Balder Knights in the church in Undead Parish for their side swords. I wanted 10, and it took me a long time to get them. I became quite good at it, of course. I can still do that quite well. Even riposte.
After that, I was (iirc) level 16, with 16 in int, str and dex, and I had spend my souls mostly on upgrading all my equipment to +5. And I was wondering what else I could do to improve it, before starting the game proper (gargoyles). Free stuff!
So, I went about everywhere I could and got all the stuff just laying around, killing all the easy semi-bosses (with maximum cheese), like the undead dragon, the hydra in the basin, the rat in the depths, Havel, the Black Knights, etc. Poison arrows, great/heavy soul arrows, pyromancy, kiting, etc.
After that, I wanted to upgrade my equipment as much as possible, so I figured out (with a lot of trial and error) the easiest way to get embers (killed the Moonlight Butterfly), upgrade materials (the Great Hollow, farming slimes, leeches and such) get to Vamos (drop down) and get souls (have the adventurers in the forest run off the cliff).
By this time I was pretty good in all those low-level things, while still just level 20 (I think, upgraded attunement to 16 as well) and with pretty decent equipment. This took me more than 100 hours. I decided to upgrade endurance to 16 as well (lvl 25), and go for the gargoyles.
Those stupid skeletons on the first floor killed me lots of times, and the gargoyles were harder than I thought, even with the good equipment. The Capra demon was even worse. The gaping demon and Querlaag required assistance.
I didn't have much stamina or health, so I went down pretty easily.
After that first round of bosses, I decided I wasn't ready yet, so I went for another round of collecting, upgrading and a bit of leveling. Ceaseless Discharge was no problem (after Googling). After that, Sen's fortress went pretty well, but Anor Londo was a showstopper.
First, the dragon arrows. I got a lucky break when the Silver Knight fell off the ledge. After reaching the next bonfire, cleaning things out and more farming and upgrading.
Lautrec killed me every time, until I found out how to cheese him. And, Ornstein and Smough killed me many, many times, even with assistance.
Well, after that I took a break, and just started it back up 3-4 times a year. I couldn't get back into it. Run around a bit, try some stuff, level up a bit, but not much progress. Lots of dying.
So, this time I did some more collecting, upgrading and leveling (of course). Pinwheel was surprisingly easy (went down in one or two casts, I just noticed after the second cast that he was already gone), but much other stuff (the archives, the Power Within) very, very hard. I think I'll try New Londo next, when I feel like it.
I like the game, I just don't have the twitch skills to excel in it. I have to take it slow and use as much cheese as possible.