
If you roll a knight, remember to increase defense, hitpoints and resistance in this particular order. As a rule of thumb, you don't rightly need to buy each and every offensive skill upgrade, except for shield bash and club stun skill. The knight is the real tank here and will be proficient at slaying lower level creatures, one at a time, while taking next to no damage.
Berzerker need to buff power, block, and accuracy. One skill point into the low level area of effect spells (AoE) is all it takes and you can just fly through monsters like they're not even there. I wouldn't recommend wasting more points than that on the skill since with the right buffs,
one can AoE large groups in 2-3 shots. Several mass effect abilities will deal damage, further enhanced by body break, which lowers enemy physical defense by up to 35. Berserkers will save you a lot of gold on repairs since armor isn't as important to them as their weapons and buffs.
Elementalists are masters of magic damage dealing from a distance and also benefit from class specific active and passive buffs to increase their intelligence, along with a very useful pet summoning. The very same pet will often enough get agro over the playing character and eventually die without dealing his steady damage over time, as it was intended. To fix this, simply start each fight with a skill attack and it is very rare for the summoned creature to require the agro.
Archers are the epitome of single target direct damage dealing from afar and you'll be surprised to notice that they can drop your health bar to dangerously low levels with just two shots on occasion. Great damage bonuses and elemental enhancements are coupled with accuracy boosts and weapon speed to grant an expedite death even to the most hardened higher level mobs. Their ability to reduce physical defense of the target also helps, effectively adding up to 40 more damage.
Rangers, on the other hand, benefit from numerous AoE oriented skills to blast away a good number of enemies at the same time. This is one thing I can't really comprehend, since AoE classes usually fare badly in PvP when it comes to small scale battles. They do get Bad Friends, which is uncanny in the dungeon settings, yet useless versus other players.
The hunter is a definite AoE class, since they present just one skill targeting multiple targets, a skill that needs to be gradually improved up to level 34, until other options become available.