I’m not an IT guy by professional, but I have or had lot of different types of sites — WordPress, Drupal, Moodle, Mediawiki, Gitea, Mastodon server etc. But I don’t understand docker, at all. With that background and compared to other apps, the easiest to start is WordPress and very close to it is Discourse. So that is not an issue, at all.
One click of DigitalOcean has some issues some times (very true with all of theirs apps) but the biggest questionmark is actually Meta itself. If poor admin has issues the first question is is this a standard setup and if the answer is yes, but it is one click of Discourse you don’t get support. Community may or may not help. But because installing Discourse is easy, if have anykind background from anything, doing it manually and spending about an hour is a good option.
Starting with bit bigger than what is announced minimum is just smart. The question of size is hard, because it depends. But starting from small and increasing the VPS when needed is an easy solution.
My piece costs on Hetzner ~15 euro a month, including tax. I had tons of content, but otherwise that community is quite small. Content doesn’t cost, except images, but users are more expensive.
I had some issues in the beginning, but I tried to use three different Discourses together several WordPresses, Moodle etc. with Varnish front of them. It worked, but handling those three forums was a bit problematic for me at that time. And when I realize that all I need is one forum and I stopped to try squeeze everything in one VPS my life got easier (yeah, I broke Varnish big time once and at that point all of my sites were down, because of all eggs and one basket).
The hardest part is building easy to use and logic structure into a forum. And with that I’ve wasted hours, a lot. But I don’t plan, I try and thinking comes later. Cleaning up unnecessary categories and sub-categories and starting use tags, and then tuning up tags, was an awful job when made by hand, ’cos I can’t use rails (or can, but I don’t know how).
So, starting a Discourse is quite easy, almost walk in a park (if mail system works). But everything else after that need thinking, understanding how users see and use things, planning and some testing. As every single system needs (and is more rarely done than backups at home).
And everything costs, but my WordPresses cost more than Discourse.