Even if you want your first "real character" to be a necromancer, I'd still cast my vote for playing something like a ranger or assassin a little bit to start to find your way around the world.

There's broadly a few reasons necromancers are hard as a newbie, which I'll outline not to dissuade you but so you understand the weaknesses you'll be trying to shore up:

1) More built-in enemies than almost anything. (But you knew that already.)

2) Area knowledge is at a premium. Things like: what creatures can you make good zombies out of in a particular set of circumstances? Where should you be hunting for useful wands or greater undead? Which areas have good places for you to set up summon traps, or traps for enemy stealth classes?

3) Aggressiveness is at a premium. In the right situation you have very strong offense; in most cases you have defense ranging from moderate to very poor. How to engineer fights so your enemies slam into the brick wall of your offense rather than the straw hut of your squishiness takes a certain amount of finesse.

4) In most cases, your value to a group that wants to get XP is marginal, so gaining levels can be a challenge.

Onto some advice:

1) Plan to join Tribunal or Empire. Both of these are more much new player friendly cabal options than Scion or Scarab. Having some players that are inclined to not kill you and possibly offer some advice will really accelerate your learning the game over being uncaballed. I mean, Empire's a bunch of evil bastards and not a pile of hugs and puppies, but better to have those evil bastards on your side and in a position where you might be able to barter for some help than not.

Granted, being Orderly limits you in some ways but at this point you need the help more than you'll suffer with that restriction.

2) Situationally, disruption (and earlier, torment spirit) are really powerful leveling tools. They won't always be relevant but don't forget about them.

3) Once in PK range, default to being invis, especially for the first ~20 levels of PK. Some people who want to kill you won't have a way to detect invis, or won't be able to keep it up 24/7.

4) Putting people to sleep and loading them up with maledictions before waking with energy drain or damage spells is probably your main PK tactic before undead start coming out, and often even after. Be aware that dwarves and other races that resist poison and/or disease will be harder to poison or crimson scourge.

5) Be wary of people who can bash or trip you -- successful command denial is hard for a lowbie necromancer to deal with.