To make the first advancement before you start off Atlantica Online, you need to go to Victoria Island. Find the ticket booth in Lith Harbour and talk to the NPC.

Warriors - Perion
Archers - Henesys
Thieves - Kerning City
Magicians - Ellinia
Pirates - Nautilus Port
However, for Pirates and Bowmen (maybe Magician) it is advisable to walk to the cities.

Bowmen: When you go to Lith Harbor, just keep taking the bottom right portals until you get to Henesys.
Pirate: Follow the directions for Bowmen but then take 3 more maps to the right and enter the bottom portal in that map.

Magician: Follow the direction for Pirates but then at the map with the pirate portal, take the top portal over the pirate portal and continue going right through the maps until you get to the town in the trees, Ellinia.

Find the job advancement NPC. In Perion, the job advancement NPC (Dances with Balrog) is at the very top portal, in Henesys, the job advancement NPC (Athena Pierce)Atlantica Gold is in Mushroom Park, at the very right inside the tree, in Kerning City, the job advancement NPC (Dark Lord) is inside a building with a sign that says 'Jazz Cafe', and in Ellinia, the job advancement NPC (Grendel the Really Old) is also at the very top (Magic Library).