I'm going to say that at even at the high school level, soccer, football, and basketball require tremendous dedication. If you're doing these for fun (aka not on school team), basketball is a good way to meet people once you're decently good. You can practice on your own just fine until you're at a level where you can join pickup games in the park. At my school swimming is the sport that anyone can do as long as they're in good enough shape, but requires early mornings and late nights. I'm going to put in a few suggestions and then address why they might be a good fit: cross country/track, tennis, and ping pong.
Track and cross country, at least at my school, are no cut. You may not run varsity, but you'll be on the team. They also get you in great shape. If you show some dedication early on, you can quickly gain some respect not just of your coaches but of your teammates as well. Just the fact that you're competing will get people to take notice of your existence. They are also fairly social--when you're running, find someone to talk to. It eases the pain by a lot and gets you into social circles. Summation: competition is fairly low below the varsity level for the most part, it gets you in great shape, and it encourages conversation.
Tennis is another option I would consider. In Europe it is viewed as an elitist sport, in America every single park has courts. What's great about tennis is that you can get good on your own--that's how I did it. I went down to my garage every single day and just hit forehands off the wall. When my parents weren't home (they couldn't stand the noise) I would hit rallies off the garage door. In a week my forehand was passable. The next week my backhand was decent. Then I went down to the courts and hit 50% serves until I could get them in. At that point, I went and found people to play tennis with. The market for average tennis players is huge. It also gets you in pretty good shape and develops your hand-eye coordination, which will help with other sports. The problem: you have to dedicate some money. Rackets aren't all that cheap, strings will break, and balls will be lost.
On that note, I'd like to point out ping pong. If you get a ping pong table with enough room around it, you will become one of the most popular people in school. Everyone loves ping pong-movie hangouts, and I mean everyone. Get yourself a table, some balls, and some paddles (yes, it will be expensive) and you'll be set. You can also practice on your own or with family (again, who doesn't like ping pong?). Getting in shape isn't the easiest with ping pong, but it will net you some popularity. It will also build hand-eye coordination.
Good luck, and congrats on taking on life's challenges!