Ultimate guide on how to make a NAS and fixing storage for good?

This summer I want to make the NAS of my dreams – being able to make an at-home cloud server without needing to pay a cloud provider a recurring charge. I would love to make a web GUI that I can add files from a source device to the target NAS and access the NAS from anywhere and any device, but I haven't ever done anything like this before. Are there any storage veterans out there that have guidance on how to make this become a reality? Thanks a bunch 👍