My one piece of advice: be cautious when it comes to sharing a girlfriend. Triads are complex. There are success stories, but even they will tell you that it was not easy, and they take work and patience. Do a search for the term "triad" and read the various threads to get an idea of some of the issues fellow polyamourists have experienced. It is rare to find a person who will love you both equally. It usually ends up with the shared woman being more into one of the two in the couple she is dating. *Enter jealousy and some other problems*
I am sure others have more to contribute.
Ry - Me. Panromantic demisexual with a history of polyamorist tendencies. Married to...
Matt (Hubby) - The once distant stranger that I complement beautifully. DH of 13 years and father of our four children.