Don't drink much. It creates problems for your health in addition to social problems. Avoid it completely if you can.
If it's a guy, I'd tell them to be in shape and try some amount of looks maxing and to really put themselves out there. Even if they are not conventionally attractive, you can have some great experiences just being an assertive, kind dude.
Of course, you don't want to give this advice to someone who is a creeper or who has a lot of other things they need to work out, but it's good advice to someone who isn't suffering from bigger problems or has a fundamentally disordered relationship with women.
It doesn't feel like it, but you can have that life you think is unattainable. You can find a wife, you can get a home, you can have a child, and there's a good chance you'll like it. You have to pick your hard, maybe you don't get to live in the capitol city and go to the club every night, but try to be consistently virtuous and you can succeed even in a world that feels stacked against you. Remember that you only exist because thousands of generations of your ancestors made it through harder times than this.
Going out clubbing is a distraction from the emptiness inside. Brew your own beer and wine and share it at events you host. Board game night, dinner parties, film viewings, craft nights etc. Much more fulfilling and cheaper. I can make 30 bottles of wine for the price of 4 drinks at a club.
Never be afraid to learn something. More than anything the world needs smart people.
Be virtuous and kind. These qualities will pay off over time.
Listen. To the people around you. To the world around you. Pay attention. When you have to speak, choose your words carefully. We have enough hot takes.
Read. Seriously, read a lot. The more you do it, the more you’ll find stuff you like.
Take care of your teeth. You only get the one permanent set, and dentistry is basically prevention and patchwork. They can’t really “fix” a problem. Also take care of your body. It gets harder to do that as you get older.
Don't listen to your teachers regarding being "realistic" with your dreams. If you want to do mechanical engineering, electronics engineering, programming, robotics, build your own machine shop, etc -- just start now. Get out of hickville where being intelligent is looked down upon.