The player is the weapon. That's the thing most people miss. How well the player player-kills is the most critical factor.
I'm always reminded of Jinroh's dwarf who had no skills practiced. He just wielded a staff and went through life. He had Trib cabal powers and a restrung nap skill. He managed to kill 9 people in the character's life, and one of them was the drillmaster in a 1 on 1. Drillmaster was played by Graatch. Jinroh, who's a friend of mine, has been behind a lot of really odd combos and gotten tons and TONS of kills. People bitch, then try the combo, and never reproduce his results.
The question is then, what do he and others like him do so well? A few things:
1. They have an idea of how their build will work and experiment to get it right.
2. They sense early if they should run.
3. They run away well.
4. They chase well. This includes knowing where their prey is likely to go, where people recall too, and just mechanically timing their steps and their attacks to not waste keystrokes.
5. Knowing the number of steps you have to take and not over or under shooting them is key. For example, used to be the Eternal Star was nine moves east of market square (or was it 14?) then south. You gain a lot of ground on people by entering exactly the right number of moves with no stacking but also as fast as the buffer can take them.
6. They have a sense of what abilities will do that is independent of forum think. They can trust their own experience, not rely on the group think of others.
7. They use the right ability for the right situation. Damage, lag, flee, low lag moves, high lag moves, sometimes no moves so you are ready to chase instantly.
8. They know where to find people. When I kill someone for the first time, I look in their bag to find out where they shop and get preps. Back when your mage only had one source for a/b/s I used to always know that for all my enemies. I killed a lot of mages in the middle of trying to get their barrier rod. People who use blowfish have a place they like to eat it... etc. Interestingly I have this data cataloged for certain players too. Back in the day I used to give Jerrotard fits because he was so easy to spot and his patterns never changed. I've killed his characters probably 50+ times just because of this strategy.
In PK this matters more than anything. Nepenthe, Marcus, Jinroh - they'll beat an average player every time no matter what they are playing.
The only way to develop this ability is to PK...a lot. I'm not as good as those guys, but I got a whole lot better when I started going balls out trying to kill people. Most people get too conservative too soon in their CF career. If you look at a post below I explained how I would rank and retrieve when I was alone against 6-15 enemies. I learned a lot that way...just trying over and over to make something work.
Four people raiding you? You can either A. not go, B. go and see if you can kill ONE. If you choose A, you might live, but you'll never improve your skills. If you choose B, eventually you'll figure out how to get one. Then two, then three, then four.
As to your more specific questions regarding gear, preps, builds and their respective advantage that knowledge is case by case and a product of the above. For example, as a shifter I value preps over gear. As a warrior, less so. I have a feel for this after years of trying to make different things work and getting in PK fights where I didn't have much chance to -win- but had a lot of chance to -learn.-
Hope that helps.