I'm in a similar position, I've been soloing for months and my highest level job is only 45 (I'm hoping to reach 50 during the current double XP event - after which I plan on just begging random folks to help me with limit break quests). It's tough because I feel like I'm so far behind everyone else and I want to catch up but the progress throughout the entire game is as DRAMATICALLY INEFFICIENT AS POSSIBLE.

My main strategy? KEEP GRINDING IN EVERYTHING.