Elliot is an alternate personality of Rue who always knows what to say, what to do, and has nothing to lose or gain.
He, conveniently, is always there with Rue doing drugs but he’s also, conveniently, unaffected by them. He’s a drug user, he does the same drugs as Rue, but they don’t control him.
Rue is dealing with her dependency on drugs and on Jules. Elliot is the manifestation of a compromise where she can comfortably have both.
However, Rue is an unreliable narrator, and given we are most likely seeing the events of the show through her depiction, Elliot’s screen time will look far different once reality hits. The opening scene of Rue dancing in the kitchen and being caught high by Gia was the foreshadowing of this. It will be a mix of Fight Club and the quaalude scene from Wolf of Wall Street.
If you rewatch the eps so far, only Jules and Rue interact with Elliot, unless he’s doing some Aladdin sht. Rue found him doing drugs alone at a party. Jules didn’t acknowledge him. The audience has been “gaslit” like Gia did. Elliot is a lie to make Rue’s behavior excusable.
What they’ll continue to do is show a very literal representation of how drugs can make you two different people.