My budget is ~500 Euro.
I haven’t built a PC in 10 years, I gave no idea where to start.
It will mostly be used to run Nextcloud, Minecraft Server and some future homelab projects.
I’m thinking of using this for the case https://www.the-diy-life.com/introducing-lab-rax-a-3d-printable-modular-10-rack-system
Where do I start? What CPU or motherboard would you recommend? I want it to be somewhat future proof and also act as a NAS
You should build the hardware around what your compute requirements dictate. A NAS needs little in the area if compute power but Minecraft could be a little demanding. Review the Minecraft server requirements and build based on that. Or build to Max out your budget and get the best you can up to that point.