-cough- -Cough-
I find archers the hardest to level up without money because they are annoying in the beginning, but if you get past lvl 30, you're on your way to smooth times.
Warriors are okay, but they make good money early game, suck 2nd job, and then make decent money (DKs made good money 3rd job, not sure if that still stands?)
Assassins can be good unfunded if you know what you're doing, so meh.
You might want to try one of the newer classes but keep in mind that you'll spend more money for just about everything since a lot of people decided to remake characters to them and some are coming back and starting them, etc, etc.
Bowmen are VERY fun if you can get past the initial stage (If you've played one before you should know that even with funding an archer is a pain in the ass until lvl 15 or so), luckily you have PQs to help you the whole way if you want to explore that option, so it's a lot easier to get through those early hell levels now.