Swordsman
As a knight you can mob monsters and kill them with nice burst skills. This will help you level quickly and you will gain money from the loot you pick up. You can use swords and spears quite effectively, and for starters, having two-handed quicken with a sword is always fun. Cons? None really, you can be effective with NPC gears. Also, elemental weapons which are wildly helpful are offered quite cheaply on this server; with some work you can purchase them and become that much more effective in PvM and more.
Crusaders are most people's choice picks. I get why, they can be fairly effective, but I still believe knights are the best option. With knights you can explore just about any map besides the party-required maps like upper level of Thanatos, and dungeons where monsters hit beginning-geared players too hard to survive like Light Halzen Biolabs Lv 3 and Thors dungeon.
Crusaders are mostly limited to maps where they can hit higher damage with grand cross. At higher levels they can do heavy damage and earn money in good undead/demon/shadow maps.