Polyamoury is an incredibly difficult thing to pull off. It's also extremely rewarding when you do.
Consider: One must cope with all the normal tensions that a relationship puts upon two people, as well as all the tensions that the outside world (or living within it) puts upon a relationship. Then consider those tensions multiplied by the number of partners that one has.
Further, consider the additional tensions caused by the relationship between one's various partners, and the demands for time that each partner makes of one. Consider the time that it takes to truly get to know each partner. Already, it begins to look a bit more difficult than a monogamous relationship.
Finally, consider the inevitable jealousy and resentment that arise in a multiple-partner relationship. No matter that they are dealt with over time; until they are completely dealt with, they add stress to the overall relationship.
Scared yet? Well, it isn't all bad.
Temper those stresses with the joy and fulfillment of finding someone to love, multiplied by the number of partners that one has. Then add in the relationships that (hopefully) develop between one's various partners. Finally, add the wonder and joy of living one's chosen lifestyle. With luck, when you solve this equation, the value will come out highly positive.
It's hard work. Some of the hardest you'll ever do. But in the end, if you can make it work, it's wonderful.