1. Inteligence - if you want to be like the other 10,000 pures out there, you don't need this, but the truly good pures have some brain..
2. Money - you'll never get anywhere PKing if you have no money...
3. Prior Knowledge - don't just jump into the wild thinking "I've watched loads of Elvemage, I'm gonna pwn em!", that'll get you knocked back to Lumb, study other players, and study your own PK habits.
4. Creativity - most of the pures out there are going to be doing the same thing...D Scim to DDS, pfft. Develop your own style, if you have Rule #1 down, you should be trying out new styles of pking, seeing which fits your economical and statwise needs.