Hello. I don't have alot of advice to offer here. But I think [I]most[I] poly relationships probably start as couples who open up and maybe that's why a single poly is viewed in a different light. I'm really trying to wrap my head around what it is you're hoping to find, not long term but as a starting point. Are you hoping to meet another poly single who already shares the same feelings as yourself? Or several? I'm just asking because I find the notion of being a poly single female interesting and, undoubtably, challenging. You are, after all, that mythical unicorn.
At the same time, try not to close yourself off to couples because of bad experiences. There are those who exist that strive for equality and not an accessory to fit into their life. I don't think it's any easier for couples to accept a third after years than it is for the joining single to feel equal.