Hey Xenith and welcome to FiestaFan!
Where to train at level 20-30? Perhaps Moonlight Tomb? I'm starting to forget where I trained at what levels... but I think I trained at Moonlight Tomb with a party.
As for making money, check out the wiki guide here:
http://www.fiestafan.com/wiki/Money_Making
There's also a few threads floating around about making money, but I think the wiki will give you an idea. xD