When dating should you devote yourself to one person or see what is out there?

I'm always focus on one chica but the women ive gone on dates are dating multiply people...How does someone accept that without getting jealous...I like this chica that ive gone on dates with but shes dating other people making me not want to open up or see the real possibilities...should i find someone whom is like me in the dating department or is it the new trend to date 3 or 4 people at a time ....hmmmm