I’d probably buy everything used other than the power supply and drives.

well a web server is a pen-testable thing, and is also a very common pen-tested thing so the background knowledge is useful .

all of the above + more???

you could use LocalAI or ollama. but neither is going to work with 300mb of ram, and it needs a bunch compute resources for response speed to be usable. these models are also not very capable, in comparison to openAI’s gpt’s, but that depends on what your goal is with the models.