Fastest way to farm level xp?

I was wondering which method would be the fastest to farm level xp, and climb the prestige tiers. High rounding? Directed mode capped at 15? Completing main quests? Playing casually to 30-40 and exfiling? Farming calling cards and completing challenges?

I'm currently sitting at 33 nebula camos, all main quests completed early, and multiple completions on both Terminus and CDM. Reached round 100 once for the dark ops, aswell as having completed around 80% of dark ops challenges. All this has gotten me to prestige 6 level 40 so far.

Genuinely interested in what methods y'all been using.