I've never had more than one parakeet, and in hindsight, I think they're happier with at least one cagemate. The one I had in graduate school, I could let out of the cage, because she didn't really seem to like flying all that much. She'd make a few passes around the room and then would land on my head or shoulder. I just put my hand in her cage with some seed in it, and let her get accustomed to sitting in my hand. Then I would stroke her with my other hand. After a couple weeks, I brought my hand out of the cage, and she'd sit on my hand or climb up my arm.
I think one thing to consider about pet birds is that some species really need a cagemate. Otherwise, they get veryy attached to their owners and can get very lonely if they're left alone too long. My grandmother always had a parakeet, and they seemed very bonded to her. Her favorite was a green and blue male, who loved to take a bath. She'd put a little plastic bathtub on the kitchen table and let him take his bath.
You will get a lot of opinions on keeping pets. How to do it, or whether it's ok to do at all. Some people believe we should never use any animal, for any purpose including, for example seeing eye dogs. Personally, I don't believe in wild-captured pets, but feel that long-domesticated species live different, but not necessarily inferior lives as pets than they would a life in the wild.