I agree that reading up and knowing things is definitely helpful, but it's only the first step in any new adventure. You have to also build up the appropriate skills you might need, and then be open and in the moment of the experiences and adapt and adjust and build new skills as needed.
I do think there is a "skill set" for successful relationships in general. Things like open, honest and non-aggressive communication, listening skills, empathy, non-judgment, acceptance, etc. These are such vital skills, yet skills that I don't think are adequately taught or supported much (at least not in the U.S.).
And I think doing your own work first is highly important as well. Knowing yourself, what you want, what you believe, and being able to identify, name, and pick apart your emotions when things go awry and figure out what the core issues are... so helpful!
I find it interesting when you see people struggling to live a poly life when they don't even really have the skills to be in a healthy relationship with ONE person. Like they expect things will magically "work out"... the poly fairy will fly in and poof! everybody will get along, nobody will ever feel hurt, unicorns will abound.