Just finished your Orientation in J1? Haha, don't worry, a lot
of people face such problems. I can safely say I'm one of them,
because I'm not exactly outgoing, and I don't usually talk to
others unless needed or the situation demands it.
For now, I'd suggest you just hang out with your OG during breaks.
If there's no real need to say anything, don't do/say anything
which you might embarass yourself with. Watch, listen and offer
some stuff at times.
You'll meet all sorts of people in life. A lot you will notice to
be shallow, but remember, that's their problem. When you say the
girls are immature, maybe it's because they're talking about things
you find to be mundane, and there has to be a Lowest Common
Denominator in conversations. Obviously, the mundane stuff will get
to everyone, and so that could be why they seem to be getting along
well with everyone else.
Your OGLs are J2s. They've got a lot of things like lectures and
tutorials to worry about, so it might make them seem aloof. I know,
because I'm a J2 myself and my OGL friends are all panicking and
fretting over work. I suppose that's what separates the good OGLs
from the rest of the heap; the ones who can worry about the new
juniors are the better ones.
Take your time. Besides, you'll be having a class to hang out with
soon, and I assure you, making friends in class is a lot easier
than socializing in your OG.