Originally Posted by Totenkopf
If you were going to get any DLC at all (not incl EC), I'd say Leviathan and From Ashes b/c they flesh out "the past" more. That said, they don't change the RGB ending a lick, so really aren't essential to figuring out the overall story. Haven't played Citadel, but hear it's nothing more than a complete distraction from the overall story (albeit a fun one, apparently). Frankly, outside of maybe adding crewmates, none of the DLC in any of the 3 games is really essential to the plotline.
From Ashes and Leviathan were the two that piqued my interest on the wiki, yeah. Maybe I'll be able to catch them in a Steam Sale of some kind in the next few weeks.