Hrm, OP seemed to take the responses as negative (which I didn't think they were either, just pragmatic/based on life experience) and decided the responses weren't to their tastes.
If you are asking if a depressed 23 yo is smart to pursue a poly relationship? I don't think it is an insane option. I was probably clinically depressed 5 years ago due to entering a relationship I was in after being poly, then becoming mono for awhile - I knew what I wanted at the time (sex that was a fun experience for both parties) and with whom I wanted it with, but I could not have the two at the same time. Led to misery for a few years. Not at all like your experiences from what I read, way back 8+ years ago with my ex-husband, I was the one who brought up poly, and he was gung-ho for the idea.
My advice is to know yourself, communicate with the important people in your life, spend time alone and ponder. That goes for any person, anytime, any relationship dynamic. If something doesn't feel good - stop. If somebody wont wait while you figure it out, fuck em.
Happiness will never come to those who fail to appreciate what they already have.