I recommend a Raspberry Pi or ODroid SBC. I started with Pis many years ago and the knowledge I gained self hosting websites on Pis opened doors for me in my career. I wasn’t even working in IT when I started with Pis, although I had an A+ cert and was trying to get my foot in the door. Now I’m a Network Administrator. I remember showing my current boss a Raspberry Pi for the first time back in 2014. He had never seen one and was very impressed. Obviously there was more to my success than the work I did on Pis, but it definitely helped me expand my capabilities and many of the skills I learned have been put to use in the organization where I am now employed. As far as having a server running in the background 24/7, when it comes to Pis and SBC, we are talking minimal power consumption and zero noise. Unless you are on the tightest of budgets and have to use dumpster-ware, an SBC is going to be your best bet to get started with self hosting in my opinion.