This leveling guide is based on my own experiences. Its different from player to player but for me, this is what I like and I tend to always be in a party. The general idea is to follow where the quests bring you. It recommended to party as much as you can because you get more experience and use up less stamina points. Partying is always better than soloing because experience is divided to all your mercenaries. Questing will provide you with most of your experience until level 95. Its been a while since I've played so I started over again with a new character. This time I can go into more detail and revisions will probably come in the future if I ever decide to make that maniac. Keep in mind that this guide is written from my experience as a PvE focused Sword, Staff, Archer, and Musician main. This will most likely be divided into 3 parts. Atlantica Level 1 to 60. Level 60 to 95. Level 95 to 120.
There is an absurd experience requirement increase at level 95. At level 95 your first 3 quests will give you a 1% bonus towards your next level no matter what quest it is. Keep this in mind so you can manipulate this by completing only 3 quests a day then farming for the rest of the time or free leaguing until the next day.
Basic Tips:
-Carry HP and MP food, it will help you train faster with less down time. They're cheap too.
-Upgrade your skills to at least 40 before level 60 you will need it. Get to 60 by level 90 if possible.
-Upgrade mercenaries ASAP, they get a good boost to all their stats. Preferably first upgrade by main level 35 (Insect Nest) and second upgrade by main level 55 (Cretan Labyrinth).
-Party and fight together whenever you can
-Use experience books on low level mercenaries rather than high level ones
-First 3 quests give 1% towards next level at level 95+
Benefits to Partying:
-Less stamina consumption
-50% per additional experience per person in the same battle
-Experience is divided to all participating characters based on level
-Bonus experience and experience books are awarded at the end of each fight
-Less likely to be targetted by King's Judgement by high level atlantica gold players
Facts about Stamina:
-At 0 stamina, drops are reduced by half and exp is reduced to a third