Welcome, your in for a great journey.

I came back to MorphOS last year after more than 10 years away and it has just blown me away with how good it is.

A MacMini is a great starting point. I started with that, then got a PowerBook and then a PowerMac G5 (you'll find you'll want the power).

Great bit is all the hardware is really cheap but the performance on MorphOS is great.