Also an older guy so I can't give you any advice about modern online dating, but
>>12079 is solid advice. I'd add that while you should definitely put yourself out there on the dating market and see what happens, at your age the best investment you can make in your sexual and romantic prospects is to focus on general self-improvement.
Get fit. Stay off the couch and develop passions and hobbies that aren't vidya. Leave your house and see the world, or at least the country, or at least the different regions of your state. Expose yourself to lots of different social situations and build up your knowledge of human nature. If you're in college, study a subject that will pay off in future income. If you're not in college (which might be the right move financially, lol) you should still be smart about money and thinking about long-term job opportunities in a trade or industry. Try and build up a little savings for the future. And get fit.
If you just graduated high school and have never had a GF, it probably feels like the odds are stacked against you. (I've been there.) The good news is that if you make it to your late 20s / early 30s as a guy with his shit together, all of a sudden the tables will be turned. Guys like us have it easy in some ways. If you shower daily and stay in shape, have interesting hobbies, don't come across as desperate and can hold a conversation like a normal human being, and you treat fat women decently and don't act like being into fat women is a shameful secret (previous poster is 100% right about this)... then suddenly, once you're pulling down a solid adult income, you'll be a hot property. Don't be too hasty to rush into monogamy at that point.
Feedism is a different story, finding a non-insane woman who's a legit feedee is a needle in a haystack and it might not happen for you.
I also 100% second
>>12079's advice to get used to breaking things off if that's what your gut is telling you to do. It hurts to reject a woman (just like it'll hurt when a woman rejects you, which will also happen), but you have to develop that thick skin. Unless kids are involved, you should never, ever get stuck in the guilt trap of feeling like you're somehow required to stay in a relationship if it doesn't make you happy.
pic unrelated