Nowadays, I spend zero time on marketing. I have a whole bunch of well-written articles on my subject. They still rank okay on Google and are evergreen. Marketing these days is word of mouth + SEO.

But for someone starting out: Write articles that teach people something (in a niche). Articles get read for many years. Social media posts go down after minutes.

Good idea. Are the articles teaching how to use your software to solve an issue people have, or do you just mention/link to the the software in the end of the article?

The latter. The articles teach people about the niche domain/subject. The app is merely mentioned as an option to make life a bit easier.

Having the graphs in the app is much easier than doing yourself.