I've been wandering aimlessly with my brother, taking on any mobs without noticing the importance of name colors. No need to say we had a mixed experience with our Berserker and Fire Mage. We were miserable.
So today I restarted a solo game, but this time I read some advices from the cubeworld forum. I rolled a rogue ninja in world seed 12345, this time knowing I have to avoid some orange and every red names, and taking on blue dungeons only.
I had an absolute blast, the 12345 world is much more beginner friendly, and the ninja class is great fun to play with the dodge and all that. In no time I could take on some named boss and dungeons and be a general badass.
That's my recommendation for beginners:
World Seed: 12345, some great low level dungeons and places (the first easier named place is dead on west of the city, it's called Darami Canyon, don't stop at Kurkor Palace).
Class: either Rogue Spec Ninja or Ranger Spec Scout (if you prefer ranged combat)
I recommend playing ninja with a 2 handed long sword, it does much better against crowds.
Avoid warriors at all cost for now, they're the weakest and most frustrating class currently, especially solo or with just 2 players.
I wish I knew all of that at the start.