Mac mini M4
If you are getting started, this is the safest recommendation. Apple's current Mac mini line starts at $599 with 16GB memory, and the 16GB/512GB retail config is easy to find. It is quiet, power-efficient, and good enough to make local AI feel real instead of theoretical.
Starter reality
This is a learning and daily-driver machine, not a "run every giant model on X" machine. That is fine. Starting smaller is usually correct.