Selfhosted

The things I paid attention to was

USB3 - you need this otherwise connecting external drives will be a joke Motherboard needs to accept up to 32 GB of RAM. Mine currently has only 8 but knowing I can upgrade is nice.
Quiet - must be silent when idle.
CPUs of less than 8th? gen will suck at video transcoding due to lacking certain capabilities. Important if running jellyfin, etc.

The beauty of self hosting is it's all about your individual circumstances so you priorities and acceptable tradeoffs will differ.

I'm running an old Igel M340C thin client to run a lot of stuff, from Jellyfin to AdguardHome. Perfectly enough.

A repurposed old PC with something like yunohost, generic Debian, or some lightweight Linux will probably get you what you need.

It heavily depends on what programs you want to run.

Do you have access to Raspberry Pi clones like Orange Pis etc? They’re often cheaper and you can order them straight from China.

A CPU that can run Linux along with some networking

Rather than give you specific recommendations, here's some guidance for parts

Mobo: The more slots you have for RAM and storage, the better.

CPU: literally anything. More cores and faster cores are ideal, but CPU requirements for these things are generally lower than a desktop.

RAM: Buy 1 stick of the fastest and highest capacity RAM your motherboard can handle. When you're ready or you start to see slowdown, buy another of the same stick. You can get far on 16-32GB, you won't need much more until later.

Storage: an SSD for the OS and one or more HDDs for storage.

PSU: generally anything in the 500-700 range will be good. You'll want more if you plan to put a GPU in, though.

I live in Brazil too and bought a R$120 old HP computer running Windows XP on MercadoLivre. Works decently enough for a Minecraft server after an upgrade (4 to 8GB of RAM). Old computers are great for price and they're good if you can upgrade them.

For general purposes, get something better than what I bought since it is not the fastest (even though it runs the Minecraft server software alright, it still lags). Maybe upgrading with an SSD would help performance.

A raspberry pi 4 or 5 and some fast USB 3 hard drives.

I run about thirty services off of an old Dell workstation that I “acquired” from my last corporate job. That includes a full Servarr stack. I’m pretty sure whatever you have will probably do the trick.

Literally any old PC is likely fine. It may be slow, it may struggle or even fail with some of the very complex software (perhaps you will encounter timeouts, or you will spend so much time waiting for memory to swap in or out to disk that it won't be worth using) but you can run Linux itself on a potato and if your machine isn't powerful enough, maybe you can get a second one and run different stuff on each, or just scale down your expectations and don't try to self-host LITERALLY everything just because you can. Certain services are very intense, others will run on a very small piece of a potato.