Just do the basic lv50 stuff that is first available to you to start getting tomestones currency such as Main Scenario roulette, and continue the path of the main scenario quests given by Minfilia. Take up the quest A Relic Reborn in North Shroud for your weapon. Keep working on GC quests till you hit maximum rank with them. As your gear level increases you can start going to higher dungeons. The crystal tower raids unlocked at the camp on the east side of Mor Dhona offer great gear to help you jump up in gear level.