Newbie here. What to take note when managing your own server?

I echo the advice already given.

• Do you really need a server? If so, do you need to manage it yourself? Are there optimization requirements that you know you need which no auto-scaling service offers?
• If you don't need to manage server instances, how they scale, where they're located..etc. you might want to go for solutions like Heroki, Firebase Cloud Functions, or Google App Engine. If you need a server and a database I normally recommend App Engine. It's relatively easy to get started there, they have a generous free tier and the backend can be in any of the supported languages here https://cloud.google.com/appengine/docs/the-appengine-environments#the_app_engine_environments
  You don't need to worry about dev ops related tasks when using something like App Engine because all is taken care of by the environment. If your service becomes popular new instances are automatically created to manage load. If you suddenly get a surge in traffic from a new country, Google automatically starts serving your content from its data center(s) closer to your users there; all of this happens without any intervention from your end.

All the best!

Don't start with a server. Start with a solution to a problem instead, make it run locally first.

Speed and iteration is more important than the tech stack. Go for a simple monolith such as a good Ruby on rails app and just deploy to heroku (there are tons of tutorial for this). This will scale fine and on its own for a while. If you're not the rails app guy, go with something you do like as long as it's a monolith (don't start with microservices). If you get this working in a local docker container, there are countless places where we can host that.

If you then have a scaling problem, there is plenty of advice. But as scaling problems are often synonymous with having many users, you would be in a luxury position (you've found some market fit). These kind of scaling problems are totally fixable and let's just address them when they arise.

Or go serverless with Firebase.

You don't need a server yet. You need a working prototype that runs on your own computer. Then you can think about hosting. And even then, a server you have to manage yourself is probably not what you're looking for.

... it might be better to use a #nocode option... right? if you don't know what you're doing with a server...