Assassin was how I learned the game back when I was a newbie.

You get:

+Class-based Detect hidden, Detect invisibility, and Darkvision.
+The ability to hide in 'civilized' and 'wilderness' areas. This means you can dictate the terms of your fights, for the most part.
+Excellent defenses (Dodge, parry, AND shield block)
+Broad weapon proficiency
+Excellent utility skillset (blinding dust, poisonsmoke, bindwounds)

I suggest you roll up an Arial (perma flight means you wont get tripped to death) assassin. Pick a neutral alignment so you have fewer restrictions on what you can kill for regear/ranking. For a Cabal, you can try Nexus (Neutral/Neutral alignment), Herald (Any alignment), or Tribunal (Lawful).

The Village can also be educational, but you lose access to all magic, such as recall/teleport potions, which will significantly impair your ability to get around the game/survive a PK. Villagers get some pretty neat abilities depending on the path you choose, but the mages you will be warring with have some skills that you may have trouble dealing with, as a new player.

Assassin tips:

Dodge is CRUCIAL. Dodge is based on DEX, and is hampered by a high carry weight. Try to keep below 50% carry weight if at all possible.

Parry is also crucial. Parry is based on STR, and is modified by the weapon you are parrying with. Swords, Staves, and Spears parry well, while daggers do not.

For equipment, look for items that give you HP, Damroll, -Saves Versus Spells, Dexterity, and Strength.

+Dex and +Str gear will help to mitigate the effects of maledicts which drop these stats, reducing your defense/offense.

I strongly suggest you go to QHCF.net, and register an account on those forums so that you have access to the item list/maps on the wiki (http://diku.qhcf.net/cgi-bin/wiki.pl).