I...find it odd, why you decided to "become" "poly-curious." Also, you're fifteen. No offense, but slow your roll. Maybe get some experience at all with either gender, before you try for both at one time?
I would go into something like this open minded, and with boundaries. If you want to have a relationship where it's all open and everyone consents, it's important to have boundaries so that people's feelings don't get hurt. Because even in open relationships, feelings like jealousy, feelings of being left out or feelings of being unwanted / unloved can still strike.
Perhaps also consider finding someone similarly minded to you to start a relationship with and then let it grow - literally - from there (because it might be a tad hard to find a group of people all at once who are interested).