I don't recommend going out and getting a second partner just for the sake of it, anymore than I ever recommend single people go out and get a first partner just for the sake of being with someone.
But, if you meet someone and they seem compatible, then sure, see if it goes somewhere. But be aware that some people just aren't capable of loving two people at once. It doesn't mean you're any less of a person, or even any less able to be happy in a polyship. It just means that you'll have to satisfy your needs in a different way.
Gralson: my husband. Auto: my girlfriend.
Zoffee: Auto's husband. Cue: Zoffee's boyfriend. Bookie: Cue's wife.
"Love is not breathlessness, it is not excitement, it is not the promulgation of promises of eternal passion. That is just being "in love" which any of us can convince ourselves we are. Love itself is what is left over when being in love has burned away, and this is both an art and a fortunate accident. " -- Louis de Bernières