The number of professional software developers is very high, even if we don't know the exact numbers. [1] 20 million seems to be a low estimate. A large fraction of those are freelance developers who are trying to sell software development services. 200,000 seems like a reasonable guess.
So clearly the strategy needs to revolve around standing out from the crowd.
One way is to pick a niche and be outstanding in that domain. Don't just be a web developer. Specialize in making sites for small volume bespoke product manufacturers/artists, or cosmetic dentists, or real estate open house pages, or something.
Then start networking. Have a card that explains your focus and hand it out at meetups. If you're one of a dozen generic web developers at the meetup, no one will think to recommend you. But if someone is talking to a friend who makes custom doormats, they will be much more likely to recommend you if your elevator pitch is about creating a web presence for local makers.
And there is no one recommendation for what you should specialize in. The entire point is to pick something that isn't already a crowded market, and if everyone just started companies based on the One Greatest Software Business Idea, it is would by definition no longer be the best idea.
My own niche violates the rules I set out above, which should give you a hint that there are multiple ways to specialize. I come in and rescue projects that are in trouble. I really don't recommend this as a gig unless you're really experienced and you are a 0.1% developer or have one on your team.
So pick your niche carefully. Talk to potential customers in any niche you are considering and verify the demand is there. Maybe look at things you've done already and decide to take your inspiration from something you already have experience in. And then take that branding on the road to meetups.
Good luck.