Finally! My turn!
I bought this game a while back and for the better part of a month I sat in this forum asking these same questions, now I get to be the wizened one. Unfortunatly, or fourtunatly depending on what you like, there are no definitive answers and anything I tell you can be legitimately countered by someone who had success doing the opposite.

I think Warrior (Shadow) is WAY easier especially if you join the old camp, which I did.
Unlike the other Gothics, so long as you hit as many quest as you can, you should have plenty of stat to fill both one and two handed and even a touch of archery and maybe even some acrobatics. I started with one and used it 99% of the time though 2 handed has it's uses late in the game.

Countless replays of G1 taught me one thing in respect to your question:

One-handed weapons all the way to the end for the easy part. Two-handed weapons don't swing that fast in G1 (even when compared to G2), and overall you do less damage with them (with only ONE exception).
Magic is sort of decent, so to speak, but I couldn't really find any practical use to it, I mean nothing special scrolls couldn't provide (mostly Ice Block).

Well... except for Uriziel's Wave of Death. Of course.

Cheers.

I finished Gothic 1 twice. Once as Old Camp bruiser and it wasn't bad. Second time I went with the Swamp Camp and made myself two handed fighter which was similarly good. My friend played as mage and apart from sucky beginning I felt he was much more powerful at the end than I ever was... Just my 2 cents.

I finally succeeded by playing as a 2-handed weapon user for the New Camp. This seems to conflict with what the people above me said, but I definitely had the easiest time with the big weapons. That's because big armor was also a part of my build and the range of the 2-handers is so wide. So the good news is that you can succeed with any class, I guess.

My main advice to you is decide what kind of character you're making right from the beginning and specialize in the stats related to that. Making a general use character makes you too weak to survive past a certain point in the game. My personal experience tells me that point is the Orc Graveyard in Chapter II. In particular, I would say pick magic or archery, but not both, as they fulfill a similar role in combat and you need to spend your learning points specializing.

My favorite way of doing things:

1. Invest in 1 handed weapons ->become shadow
2. Don't invest all the points into stuff you don't need right now. Become a guard in the old camp.
3. Use all of your saved points to become a mage. You will get the chance to become a mage even if you are a guard of the old camp.
4. Kill everything with wave of death :D

Played as a mage a few times but never did use that wave of death. Maybe why I had such a hard time :)

One thing you'll notice, playing the Gothic games, to succeed as a mage you have to stockpile skill points without using them, which makes you much less powerful as you progress. Magic is somewhat better (from my experience) in Gothic 1 because of the absurdly cheap cost of spells, but it still takes a bit of work to get there.

Also, even as a mage you'll likely find yourself in melee combat on occasion.

If I'm not totally mistaken you need to master one-handed weapons to even start two-handed weapon training... and if that holds true then IMO EVERY character in Gothic 1 should get at LEAST level 1 in one-handed weapon fighting(Assuming you aren't role-playing or something like that).

Honestly bows (this very likely applies to crossbows as well) are probably the weakest path you can take. The fact that dexterity doesn't contribute to damage makes it so some enemies will barely be tickled by the majority of bow attacks in the game.

Strength is really easy to pump, so melee becomes exceedingly powerful (though you still have to be careful of getting surrounded, depending on your armor class).

Actually you don't. I don't know if that applies to G2 but G1 for sure you don't.

Okay, thanks for clarifying that :D Not sure why I thought it did.

EDIT: Look Below.

Had to amend this, because I couldn't figure out why Cor Angar wasn't teaching me two-handed weapon combat...

Lee is the only one of the 3 teachers who teaches 2-handed weapon combat without having mastered 1-handed weapon combat. It's actually a bug.

So unless you're going New Camp, EVERYONE should get 1-handed weapon combat.

(Didn't mean to double-post, sorry)

Don't sweat the double post, I didn't realize that, thanks. :D

I guess I just assumed via who I went to first. Guess I won't be writing any walkthroughs or strategy guides. :P

Lol, no worries. It's an understandable assumption.