Welcome to the endless rabbit hole that is self hosting!

I think the best advice I could give is keep it simple, just add one piece at a time, and take notes.

Personally I would stay away from youtube. Get used to reading installation instructions from the source and documentation, it is a valuable skill. Then come here and ask questions if you run into problems. Pihole is a great place to start, it looks pretty begginer friendly (I have not run it personally, but I just read through some docs)

I also started with pi way back when, and honestly it adds one more thing you have to learn about while you're trying to learn about hosting. It's not too bad, especially if you dont mind the command line, but you could get your hands on an old laptop or desktop for cheaper. In fact everything I use runs on a $30 desktop from 2015 (I did upgrade it a bit lol) and my rpi4 is sitting in the corner collecting dust. A more familiar interface will make troubleshooting less frustrating. I find the desktop runs a lot better than the pi too.

There's so much to learn and you will probably feel overwhelmed at times, it will pass though, just stick with it.