You need to do the required quest when you want to get nation at level (Cabal Alz) 52. There have many quests for you can do with your level up. So you need to choose to do or not to do for your character.
First you need to do all quest about the truth of the research group, the books of apocalypse part one, the books of apocalypse part two, the books of apocalypse part three. You need to do the first quest of sage tower which appointment of 8th sage. You need to do The Wizard's Laboratory Part 2 from the secret organization part two. And last you need to do quest until Sacrifice quest on the Sword of the Guardian and Prelude in Cabal.
It is easy for you to level when you are level (Cabal Online Alz) 52. If you like to choose other quest to do but you had better not to do this quest: The Chasing Spy, Thief Guild, Mutated Jungle, Strange Phenomenon and Rebellion of the Thief Guild.