The first black knight was guarding the ring. Bl Knight gear usually has a required 20 Str to wear. Later in the game you fight more that respawn.
Did you go to Undead Burg? You're supposed to be there. Also don't worry about heavy gear yet. You speed is most important atm. What stats are you leveling up?
Mainly Endurance for that precious stamina, and Strength to wear crap. I did level my Faith to 14 so I could wear the Astora Short Sword, but then I got the Drake Sword which is quite obviously better.
I might level up my Vitality in a bit, but I find that I take such massive damage from attacks that putting 10 points into that to increase my health by 20% just doesn't seem worth it right now. So mainly I'm just pumping up my Endurance, and otherwise putting stats into stuff to wear better gear.
Right now I've got:
14 faith (might go to 16 to use that one miracle)
everything else is base stats I think (Knight).
I put my dex to 15 to use the winged spear which was really good in Demon's Souls, but doesn't seem that great this time. Still, I guess it's not too much of a waste, usually you need 16-18 dex for good stuff anyway.
Right now I'm trying to find a good shield with decent stability so I don't feel like I'm wasting my time leveling it up. Pretty much the main problem I have with the game is that when I block attacks from powerful things, it just blows through my guard completely and one hits me. So I need a better shield. I don't like relying on dodging too much in this game since it can be very spotty and just fail you randomly. Best shields I have now are the dragon crest shield and the hollow warrior shield. Dragon Shield has better resistances, but the hollow warrior shield has the best stability I've found yet. Sadly.