Looking into a poverty build

Yep, another poverty post! Last time I asked something similar it got downvoted to hell. I got a 3D printer and a fixation on piecing stuff together. The only thing I don't have is money to drop on a pvs14. I could get an nvg-30, and am still considering it, but then I wouldn't have a project to keep me entertained on my free time.

My questions are what can I 3D print? What can't I? How much money would I be saving on printing? What parts can I somewhat cheap out on? What parts can I absolutely not.