The easiest way to start running locally is to download LM studio.
It is not in the terminal so its not intimidating to get started. Any computer is powerful enough to run the most basic AI models which you can download from in the app. You can start with a 1b or 3b parameter model and then expand from there depending on what hardware you have.
As for buying hardware the sky is the limit. If you have a gaming PC you can run it on that and you should be able to get up to a 13b parameter model going.
For custom hardware its not released yet but I will be keeping my eye on this when it comes out.
"Nvidia announces $3,000 personal AI supercomputer called DigitsThe desktop-sized system can handle AI models with up to 200 billion parameters."
https://www.theverge.com/2025/1/6/24337530/nvidia-ces-digits-super-computer-ai