Let me start by saying relationships are hard work, whatever way you chose.
My gf and I have been together for 3 years, and have a poly relationship, and it´s great! Often when talking about polygamy (or polyamory), people will say it seems very complicated, but which relationship isn´t? It´s just hard to find a long term sucessful relationship, period.
Personally I`ve known that poly was the way for me for long. In my previous main relationship, I once saw my ex looking at another guy, some friend, and I knew she was into him. I told her that I wouldn`t mind if she wanted to be with another guy, as long as she talked to me about it and we were upfront about it, be respectful, not do anything behind the back etc. She got really angry at me for even suggesting that, saying I must not love her if I think this way, etc etc.. Irony of the situation is that eventually she actually did get together with that guy behind my back, acted in a really negative way, and left me. I was devastated, but it just confirmed my idea that the issue is lack of respect, doing behind the back, lying to oneself and to the other, etc.
Then I had a quick relationship with a girl that was really into me and wanted to do whatever I said, which was not healthy. She actually did not want the poly thing, but she would have accepted just for me. And I felt that was not right, it has to be balanced, so I eventually broke up with this girl, thinking that if I continued I`d hurt her more in the future and it wasnt fair.
So now with my current gf we have it very good because we are both equally open to it. I won´t lie to you, it was not always easy, but that`s important! Having a poly relationship necessarily means you must work out your insecurities, your fears. These things need to be brought up, talked about, worked out. And this makes an amazing opportunity for personal growth! You gotta be prepared for that, don`t expect that it will all be easy going sexy sexy time and fantasy realizations

But it pays off big time IME!
All the details have to be worked out with each person, its not like you can make a `one-size-fits-all´ plan where its like: ¨ok you screw anybody and so do I¨. At least that´s not how it is for us. We are definitely open that the other is with someone else, but it depends who, when, how, etc. Once fo example there was this guy who was a guy I did´t trust, and was trying to be with my gf. She had some attraction to him but she understood why I felt weird around him, and she did not continue going out with him. On the opposite side, I had a great friend that actually got together with my gf and it was flowing very well because I knew he would take care of her, not treat her bad, etc. I´ve also been with a girl she didn´t like, and another girl she didn´t mind. So far we did not have a threesome, it was always a separate thing, each one of us with our respective poly lovers, but who knows what the future may bring.
Also there are situations and situations. For example, maybe you decide that the relationship is open only when you are physically appart (during a travel, etc). Or maybe you decide the other person can only have a secondary role. Or maybe the person joins equally. etc etc. So many ways to go about this. The most important is that you talk to your partner about it, and find what works for both in each moment, with each other potential partner.
Many things to say, but ´ll leave it at that for now. Feel free to ask any question, maybe I can answer from my limited experience
