Limited theory
Not trap based
Principled
Long term
Unfortunately I don't think an opening like that exists. Ultimately chess is not an easy game
I think the Scandinavian as black (and scotch or scotch gambit as white) is great for limited theory. It's not trap based (mostly) and you can probably play it a long time. That may be close.
What do you all think is the best way to start out as a beginner? I'm trying to teach a beginner to focus on the other sides of chess rather than the opening, so a repertoire without much theory would be great. I also want something principled, not something trappy or offbeat. That way it can be a long-term repertoire rather than a trappy one which only works in the beginner level, but no more than that.