thief is good if you want to take one of the other starting gifts along with the master key (which is the best one, imo). the class you pick at the start is essentially irrelevant, a knight can dodge as well as a thief if you strip down his armour and weapons a bit. what i suggest you do is pick a weapon you really like and build solely around that - level your strength up enough to one hand wield it then ignore all of your other stats barring endurance and vitality, since points in anything else are essentially worthless if you only use one or two weapons of a similar class. SL120 is generally the 'cutoff' point for levelling (i think, unless the meta has changed) for pvp, and frankly it shouldn't be necessary after that point anyway. as peeps have said, equipment > level, and skill > all. there are naked sl1 playthroughs on youtube, if i am not mistaken, so with enough leet skillz you can overcome anything.
and if you have a shield, dear god walk everywhere with it raised. drop it in combat between hits that you take or rolls though, as this lets your stamina regenerate far, far faster than if you kept it up all the time. once you get a feel for enemies' natural rhythms, you know roughly when it's safe to drop the shield and catch your breath. and don't try to parry anything twice as long as you are, it probably won't work.
i most recently beat him as thief with an estoc you can find very close to firelink shrine, just poking him from behind a shield. took me 2 or 3 goes i think. first playthrough i was hyper over-levelled so i killed him really quickly with a zweihander.
