Making new friends is never a conscious effort on my part, so I have never really thought too deeply about what I get out of it. It just sort of seems to happen when I least expect it, but then afterwards I'm almost always glad it did. Maintaining friendships is definitely a rewarding experience, even if I can be a bit too enthusiastic about it at times. When I make a new friend I generally wanna hang out with them all the time and it sometimes comes at the expense of maintaining the other relationships in my life. I guess with every person the friendship experience is different. You do different things, have different conversations, and it renews you a bit. It makes you different too. That's what I get out of it, anyway.
As for romantic relationships, I'll let you know when I have one