Debian is molded to the server domain pretty closely; Red Hat / Rocky is ideal in regulatory environments; Alpine when the priority is to be lightweight and reliable; I run Void on my personal machines because it's the most BSD of the Linuxes and stays out of my way when I need to do weird stuff.
If you're a beginner, you can append 'ubuntu' to your google searches instead of 'linux' and get an answer that makes sense. You'll know when to move on from ubuntu when you have to search 'foo bar linux' to get a usable answer.
But for someone who might have some Ubuntu experience and little other Linux experience, running an Ubuntu server might lead to fewer surprises. Ubuntus do ship with things that Debians don't have. I can't name any, since I don't use Ubuntu, but they're the things about which you either say "how nice!" or "how dull!"
What may not be good about Ubuntu for some is that it's too bloated and not difficult to learn for someone who wants to hang their hat on that.
Moving from Ubuntu to another Debian installation, including debian is no big deal.
P.s. as an alternative to ubuntu you could check Alpine Linux (for both root vps and containers)
Good luck!
1. Digital Ocean offer small VPS for $5 per month. That's a 50% saving right away!
2. Stick with Ubuntu in the beginning. It's not the best, but it's 100% good enough and has so much support and tutorials out there.
3. If you have a small VPS with not much RAM, definitely set up a swapfile. It gives you virtual RAM for doing RAM heavy things on a small VPS.
4. Use the virtual firewalls offered by your host rather than the server firewalls in the beginning. If you mess up a server firewall you may have to get your host to reset it for you. If you mess up a virtual firewall you can amend it through a web UI and get back to doing things quickly.
5. Learn to read man pages and log files. Between the two you can figure out how to do stuff, and then figure out why it isn't working correctly.
6. In terms of security, use a recent distro, use a firewall close everything you don't need, use SSH keys, and set up secure passwords for everything else, and you will avoid a lot of problems.
7. Keep an eye on resources, programs like top, uptime, free, df, and du will allow you to see what's using up CPU, RAM, or disk space.
8. Learn a relational database. MySQL or Postgres are good choices. This skill will keep you employed for years, almost every business uses a relational database in one way or another!
9. Have fun :)