Considering I have 5 characters so far, I can say I have a lot of experience lmao
Myself I would do story until Titan is open with both of the fast travels unlocked, then do public events (and lost sectors of there is time between public events) there until level 14 or so, then finish the story.
Titan is the best for farming public events because there are only two places, so there is usually people around to help out, and the lost sectors aren’t hard =]