Shattered Kingdoms

I think there's two important facets to what makes classes newbie-friendly: difficulty and instruction. Difficulty includes survivability, preparation, and intuitiveness. Barbarians are tanky, require very little preparation to function on a basic level, and extremely straightforward. Hellions are very survivable (hide/sneak/invis, dominate for a mediocre meat wall, rift/word of recall), but require a lot of preparation and are probably the least intuitive class we have. Instruction includes usefulness to others and motivation to learn. Priests are extremely useful to others and stand to gain a lot by learning about the game (staves, scrolls). MR barbarians are useful to others, but they don't really have much motivation (at least not immediately) to learn. What does an MR barb need to know about saves, or enchanting? "Put more armor protection on all my armor," assuming it's not a griffon. They don't need to know how to get buffs, they don't need to learn what buffs can do for them, they don't need to know where to find armor with innate saves, etc.

Note: everyone stands to gain something by learning about the game, obviously. The more informed you are, the better. Some classes, however, stand to gain more by learning than others.

I also think it's more important to consider PvE than PvP for newbie classes. PvP is still important, but before you stop dying to Finney you have to stop dying to tigers (and before you stop dying to tigers you have to get Edoras to stop [REDACTED] zapping himself).

I would actually not recommend an MR barbarian to a newbie for a few reasons. They're less tanky than normal barbarians because they lack access to buffing spells, and they're more difficult to heal. They're also going to be less encouraged to learn, and less exposed to things that they need to learn about. That's not to say that an MR barb can't learn how to use defensive and offensive buffs by watching and asking, but he's a lot less likely to do that if he doesn't stand to gain any immediate benefit. It's not a disastrous choice, but I don't think I'd recommend it. A normal barbarian is totally newbie-friendly, though.

Shamans are pretty newbie-friendly, and while they don't have enough stat points to max everything they want, they have enough to fill either the tanking or spellcasting roles. They don't die easily to NPCs, they don't need much preparation because they can buff and heal themselves, and on a basic level they're pretty easy to grasp. They're also useful for brewing and healing, which means people will ask them for help and probably end up teaching them in the process. Their access to buffs AND debuffs means they have an easy way to learn what buffing and debuffing can do, and they can benefit immediately from learning. Unfortunately, only Syn and OA like them, and nobody likes Syn or OA because they bathe irregularly. Priests are simpler, and can't tank but have even better supporting and utility spells. Supporting your group takes a lot of situational awareness, but that's not that difficult to learn.

Warlocks are a wonderful PvE class that can support a group and have access to some defensive tools that can make life a lot easier. They don't tend to die to NPCs, they don't need a whole lot of preparation, and they're nice to have along. They level pretty quickly (I think), and most of their tools are very easy to use (how hard is it to cast magma on somebody squishy?). They're not the scariest class in PvP, but most newbies aren't going to learn how to use their first character to its fullest potential anyways...right? It's not just me? It might just be me. I suck.

Scouts are a fantastic first class and I'd probably recommend them first to any newbie unless they were dead-set on playing a melee or spellcasting character. Between tame, stealth, and healing herbs, they're pretty good at not dying. They're very self-sufficient in most regards, but they also benefit from good preparation and they can offer a lot of utility to other classes. They aren't the most dangerous PvP class, but they can play the NPC wars game pretty damn well once they learn where the good tames are and if they join a tribunal (not to mention buffing their pets and guards), and they can fight with attrition very well. The main problem, at least for newbies, is their weaponry: they have to find out which weapons can reach, and ranged combat has a lot of extra stuff you need to know about like size, weather conditions, and bow/arrow combinations before you can really do anything with it.

For newbies, I would recommend normal barbarians, shamans, warlocks, priests or scouts. I would especially recommend priests and scouts. I would recommend against necromancers, paladins, hellions, or bards. I would neither recommend nor recommend against mercenaries (similar to barbarians but they need more prep), MR barbs (it's harder to babysit someone who is immune to magic), swashbucklers (only because they're easy), rogues (easy but they need prep to be effective), or sorcerers (obviously the most powerful class, but they take a lot of knowledge about the game).

Of course, I suck, so there's that too. I still can't lead a group to ToM X_X

If your goal is to quickly become one of SKs elite players, your first character should be a sorc. My first character was a sorc and I learned how to be a boss really quickly. They're the best for exploring and learning about the game (locate object, charm, gate, etherealform, invis, fly etc). They're helpful and will end up with lots of friends to teach them (shrink/enlarge, enchant, locate object, gate, etc).

They are the most survivable thing in the game. They get wands, etherealform, detections, mirror image, permanent access to the third row, and locate object. Unless your enemy is some [REDACTED] voodoo shaman, there's nothing you could be that is better at not dying. It will take a little bit of time learning to achieve this unkillability though.

And any moron can be effective in pvp with a sorc. Well, I mean, with proper direction, anyways. I can think of a lot of sorcs who were just plain [REDACTED] in pvp and died all the time. But if you hold MI, stay third row, and cast charm at people, you're good. Cast charm until you're meat shield is dead or you are getting hurt by something, then recall/zap etherealform. MR opponents will present some difficulty due to AoN cancelling charm (I assume).

So for learning they are the bees knees, and for survivability they are straight up killer bosses.

They are entirely self-sufficient and can solo most areas. People say they take a lot of prep work but only if you are spending your time hunting down elite items you don't actually need. They don't need more prep work than other classes. So they're scoring well in preparation department.

As far as intuition goes, sorc was my first and I had no trouble figuring out how to get in the third row, hold MI, and cast charm at people. There's a ton more that the class can do, but if you start with this as your baseline, you're solid. You will learn more advanced things later and become king of sk.