Hi and welcome!
Trios can be very tricky, as they are the constellation you are most likely to end up with an outsider problem more often than not!
I would recommend to either go straight up to four girls and introduce a bonded couple of sows of a different age/size to avoid major dominance issues and outsider problems (as each of them has already got a friend) or think about adding a neutered boar. How old are your girls? Younger sows will usually accept a boar, but you may have problems with older, dominant girls - they may not like to share the leadership with a boar! You will usually know within 20 minutes of the first meeting whether a boar has been accepted ot not.
I have dated my two 3 year old cataract sows at a rescue that has neutered boars with great success last summer. It was well worth the extra effort to make sure that they all gel! Thankfully, for once they liked my favourite candidate and we came back home with boar #1. If not, I would have made the rounds of all rescues within my reach that have already neutered boars... rolleyes
Whereabouts are you?
