Expand your social circle in Romania

To have the best chances, you need to speak Romanian well since it's the native language here.

However, social circles I'd say are usually formed here from family relationships; or the "colleagues" relationships, whether it be from a workplace or school/university.  My wife still has get togethers with friends from university or her former workplace from many years ago, even though they really have nothing in common anymore.  It baffles me.  For some reason, they rather hold on to these social ties (and memories of what once was) for life and death rather than venture out and try to meet new people that might be more relevant or compatible to where they are now in their lives.  With that said, I think it can be quite hard to penetrate or form new social circles with locals.  It's more likely that you'll be seen as merely an acquaintance, no matter how pleasant they may act.  I've found that pretty much the first question that comes up when meeting a new person in a social setting here is "where do you work/where do you go to school"?  It's a normal question and nothing unusual, except the intent is not just polite interest or a conversation starter, but mainly to ascertain your social/economic status for profiling purposes ("What can this person do for me? How can I use them? Are they above or below my own status".  If they don't find you "useful" to helping them get something, don't plan on seeing or hearing from them much or developing any real friendship.  Unfortunately, I see this behaviour taught to and displayed by small kids here.  So, this mentality starts early.

I'd say it's certainly easier if you stay in the expat bubble, forming circles and socializing with other expats mainly.  Of course, you'll be limiting yourself; but in places like Bucuresti where the expat numbers are quite sizable, it's enough to get by or start with perhaps.

If one thinks they can just drop into a locality, society, country and immediately be welcomed and accepted, they're probably in for a harsh reality check.  You'll have to work, persist, and expect still not to be accepted.  A LOT of people here just don't want to accept outsiders, unless you really can do something for them.

Romaniac

Like the moderator above posted learning the language will definitely help you more than anything. While a lot of people here do speak English and some other languages to a lesser degree knowing Romanian will give you the greatest chances of quickly gaining friends.

I disagree with the moderator on just about everything else he said.  There a crappy people everywhere and good people everywhere.  I haven't had problems finding social circles and I have made very little effort.  If you move here with a partner you may find friends from that circle. I spend a fair amount of time with my bother in law and less with my sister in law but have made no real friends with anyone from their circles. 

Just be yourself.  Don't be afraid to talk with people. Get involved in things that interest you.  If you like to work out go to the gym.  I have dogs so I commonly meet others with dogs when walking and at the dog park.  I found a friend from there and met another though him.  I meet at the gym with them 3 times a week, we message each other when we go outside with our dogs, we go for beers, and were planning a camping trip but I will be out of the country now.  I am also a nerd and like gaming so I just looked up weekly events in București and signed up.  I now meet with that group twice a week and go for beers with one of the guys from there.
Just talk with people and find people you have things in common with.  People are friendly here in general. I have had very few negative encounters with others.  If you are a jerk you will surely have problems finding friends if not you will be fine.
Good luck!!!