TL;DR - If I could restart at 18, I'd build things AND spend an hour writing about the grind. Your first projects will be bad. Document them anyway.
If I could start my journey again as an 18-year-old coder, here's what I'd do: build stuff, and then spend one hour marketing myself - on LinkedIn, on my own website. Writing about the grind, not about the technology. Your first projects will be shit. Doesn't matter. Show how you're trying.
I've been coding since 2021. Now it's 2026: I bought my dream car, I make good money, and I'm in a state where I can wake up and work on things that matter to me, at high volume. When you document the journey, you can look back and see how far you've come - especially on the days when things go wrong.
People will say you're bad. You are bad now. You'll be good if you do it for years. Their opinion changes nothing about that math, so ignore it.
Put yourself out there - a portfolio, articles, LinkedIn, X. Don't be afraid of being visible on the internet. I was afraid, and it cost me years. That's exactly why I'm writing this.
Start at 18 and I promise you'll be happy you did.