Welcome to the game!

I'm also a planner. Probably to a fault. And I've played moderately successful characters in each of those three classes.

For a new player I would not recommend thief, for these reasons:

1. Thieves benefit greatly from scrolls, IMO, so not knowing those items may hamstring you to a certain degree.

2. Picking thief skills is sort of complicated, especially if you decide to mix paths. Some of them "sound good" from the help files but are, IMO, not worthwhile.

3. If you plan to rank all the way to level 51, which I recommend, then your thief will have serious difficulty killing most opponents. They're also fairly fragile. You can mitigate that fragility by taking shield block and acrobatics, but both of those cost thief points, meaning you're giving up other skills that are much more useful from a "PK offense" point of view.

4. Thief skills cost thief points. Generally speaking, the more skills you have the more deadly you are. One way to get more thief points is through the devious versatility edge, which is expensive in terms of "edge points". Edge points are earned from immortal given xp, exploration xp and observation xp. As a new player, you may have a tougher time accumulating edge points, which may mean you'll end up working with fewer thief points than other thieves.

As for races, if you choose to do a thief, then I'd recommend human or arial. Arial mostly for the perma-flight.

Assassin and ranger are both decent choices for a first-time player, in my opinion. Note, however, that the different ranger paths play very differently.

Ranger disadvantages:

1. They are pretty gimped when fighting outside the wilderness, and many people will flee immediately when they encounter you in the wilderness. The ones that don't flee are the ones who are buff enough to actually beat you there.

2. They greatly benefit from certain talismans, so if you don't know these or will have a hard time keeping them on hand (because its time consuming for you to accumulate gold) then your ranger may have a tougher time with PK than other rangers.

Ranger advantages:

1. When you're camo'd in the woods typically the only people who can see you are people who aren't your enemies. This isn't always the case, but most of the time it is. So its usually possible for you to rest or go AFK in reasonable safety.

2. Wilderness familarity, ranger weapon, camp, and herbs make ranking relatively easy.

3. Depending on your build, PK has the potential to be really, really, really straightforward. So in that sense its a good way to "get your feet wet" without becoming utterly frustrated by the PK aspect of the game.

With regard to specializations, I'd recommend Survivalist or Savage, and either Forester or Mountaineer for terrain. Each specialization and home terrain choice adds and subtracts certain skills/spells. With respect to race, I'd recommend felar or cloud giant. Felar gives you claw attacks while wielding a ranger weapon. Cloud giant gives you the best possible bearcharge, and the ability to take edges that juice your ambush damage. Cloud giants have the disadvantage of occasionally stepping out of cover when creeping, though, due to their size.

Assassin advantages:

1. With "assassin detect hidden" and built-in detect invis, you can see a lot of people. You also don't have to buy detect invis preps.

2. With "assassin hide" you can hide from a lot of people. When you hide in the woods, duergar and thieves can't see you. (But rangers can).

3. Generally less fragile than a thief, especially when you get martial trance.

4. Assassinate gives you the possibility of killing characters who would otherwise be nigh-unkillable. (That is, if they give you the opportunity to stalk them.)

5. You can't zap, brandish or recite, so the range of preps you have to keep on hand is slightly smaller than for a thief/ranger.

Assassin disadvantages:

1. You have to spam up each kick, in order, to get the next one. This isn't a big deal, but some people find it annoying.

2. When you lose the advantage of stealth, e.g. against duergar warriors and thieves, you are often at a disadvantage. Especially pre-martial-trance.

3. You don't have any skill that can perma-lag someone. You do have lots of skills that render melee characters mostly useless in combat. So you may find it frustrating when they just "leave" after you break all their bones.

With respect to race, I'd recommend arial, human or felar. Arial gives you the best dexterity and perma-flight. Felar lets you wield spears and staffs and still get claw attacks, which can be useful when fighting classes that don't learn one of those weapons (e.g. anti-paladin, thief, bard, shaman, orc). Human has the lowest exp-penalty and no vulnerabilities, so your PK range will generally be more favorable.