Do not play a good. Under any circumstance. Do an evil at all costs.
It doesn't really matter what you play - pick something you think sounds cool and just play. Its your first character so you're going to be learning no matter what you pick.
However - I would do a human DK. Detect invis and summon mean you don't need to go stupid running about to gather consumable and DKs are great in the PK power department.
Be prepared to die though. The more experienced players (and even the less experienced players) are going to be able to kill you. Make sure you learn from dying because that will make you better faster.
Finally, listen up chump!!!! Plan on getting to lv 50 because there is no point PKing much below this rank or doing much of anything. You can't experience 80% of the game before you're pinnacle (or close to it). The ONLY way to learn to play is simply to jump in the deep end and play. I did this and so did a lot of the guys I used to know. We all became decently strong (some insanely strong) players. Everyone I know who was 'easing themselves into it' is still 'easing themself into it.' And they all suck.
Cheers,
L-A