Take my advice with a big grain of salt because I'm by no means an expert at finding customers. I can just say what's worked for me.
The thing that's been successful for me is to figure out who my customers are and find ways to show them I have something valuable to offer.
My most successful example was TinyPilot, where I wrote about how I built the first prototype,[0] and that post had an extremely positive reception on HN[1] and reddit[2]. I continued writing about my homelab because readers who were interested in learning about homelab were also people who had a use for TinyPilot.
I did the same thing when making my blogging course a few years ago. I joined a community for developer bloggers and gave people constructive feedback when they'd ask for notes on their drafts. Then, I approached the community manager and asked to pilot the course in the community for free (she actually insisted on paying me because she didn't believe in asking for free work). But the community liked it, the manager liked it, and it was great for me because it gave me feedback and testimonials for my course.
I've used ads but never as a first step. I think the first step has to be highly personalized where I'm out there meeting customers where they are and showing I can offer something useful.
1000 true fans
and Seth Godin's approach to marketing - that you should focus on the smallest group of people in your market and amaze them
These concepts helped me a lot with marketing to consumers and SMBs
Also, follow @mtlynch's content - even though he says he's not an expert, I feel that atleast regarding marketing to devs and builders - he is one of the best out there
Do you have advice on finding first clients? Especially in B2C?
Throwing money on ads seems tempting because it’s such an easy way to reach clients but I’m not sure about “quality” off the clients.