I'm going to give you some full-spectrum advice I wish someone had given me when I was your age. So, imagine 16-year-old AD -- we'll call him Addie, because
of course he'd be named that. No fashion sense. Overweight. Really into video games, being a virgin, classical mythology, feeling smarter than everyone else, Dungeons & Dragons, and Ayn Rand. I have no idea if you're anything like Kid!Me, but let's hope not, because it takes a lot of effort to blossom into what your goal is: becoming a
real human person.
Most people will tell you that high school doesn't matter. And it doesn't, except this is where most functioning adults learn to perfect lifelong skills, which is exactly what you're trying to do. Your goal isn't to peak at 16. Your goal is to be fucking amazing when you're 25+. Anyway, here goes:
(1): Learn how to cook. You'd be shocked and appalled how many adults can't cook for themselves, and when you eventually do invite a girl over to your apartment, I cannot stress enough how ridiculous a freezer full of Hot Pockets looks. This year, I went from complete moron to regularly cooking for my girlfriend. Cooking together is a fun activity.
(2): Learn how to be healthy. I used to eat an entire large pizza and, because it had mushrooms, I thought it was healthy. The fact that you're already exploring this now is laudable, because now's the time to make lifelong changes. If you want to lose weight, I suggest weightlifting, maybe something basic like StrongLifts 5x5. That, combined with healthy eating, will fix you, because weight management is a
long-term commitment and needs to be sustained throughout your entire life.
(3): Get a hobby, or two, especially one that's universally accessible. Despite a lot of fedora-wearing misfits decrying small talk, it's everywhere, and it's the first stage of human interaction. Being able to talk basketball at my barbershop is actually convenient. Other hobbies are good too, especially when there's something you're passionate about. That requires trying new things all the fucking time.
I didn't know how much I'd enjoy cooking until I actually did it. Now I splurge on sous vide machines and Nutribullets, and I have actual spices. A year ago, it was Lean Pockets and Greek yogurt. Sad children blossom into sad adults without some course correction.
It's perfectly okay to have games as hobbies, but well-rounded, interesting people have more than that. They do more than that. Being able to "cross-train" is a useful Lifehack: I'm replaying Pokemon FireRed in Portuguese and I've played through several RPGs in Japanese and others in French. Being able to combine language practice with gaming has really benefited me.
(4): Travel, to some degree, as often as possible. Everyone's interesting stories happened elsewhere, whether it was Vegas, on a road trip, or in Europe. Vigilantly guard yourself against sameyness. You may fall into ruts. Don't let those ruts last too long.
(5): Make lists of what you need to accomplish. Include "self-improvement" goals on those lists. For me, right now, it's language study, "read one chapter of a book," and touch one job-related item each day. It's all about building good habits, and your goal is to make these things second nature.
(6): For conversation, just listen. You don't need a book (although
How to Win Friends and Influence People wouldn't be bad), just the ability to listen empathetically. But here, read this
summary and see what you think.
I think that covers things. Anyway, you're already caring about the long-term choices you're making, so I think you'll be all right. Focus on your education and remember that any growing you do now in high school (where nothing really matters except getting into college) will pay dividends later on. Good luck!