You're best bet is to play something that you want to play. Have some fun. If you're going to do a mage, pick one that sounds cool and go with that.
The truth is - no matter what you play, no matter how survivable it is you are going to die sometime. If you pick something that is fun you will have a LOT more enjoyment while playing. Trust me - I've played 'power' race/class/cabal combo's that were never fun and they never do as well as anything I've rolled that I really wanted to play becaue it was cool 
If you want to be a necro, be a necro. Rank up, ask people how you can kill others - they will tell you. Make some friends, ask about what things you should wear - people will help you. I found the best way (esp once you get to lvl 50) is to get a group and ask to take you and get something that will help you. THen get something for them. Then something for them and so on.. If you watch carefully (and use a client than can log) you will learn fairly quickly how to get some pretty nifty equipment.
PK just takes time - if you want to be good at it just start killing people. It doesn't matter if you die - we all die. Hell, I died just the other day and I've been playing here for years.
The best thing you can ever do is just play things that are fun - and if things get stressful and don't go your way just log off. Don't delete your characters, just log off, cool down and remember why it was fun to play. The fun will come back. 
Cheers,
L-A