I have one of these that I got over six months back.

https://www.seeedstudio.com/SenseCAP-M4-Sqaure-Bundle.html

That I no longer need. This is used to do mining of Flux and Helium. Flux does not need any antenna, but if you decide to use Helium you might need an indoor antenna or outdoor one depending on how you want to setup. You can get them from gowifi.

Pick up in flat bush or ellerslie. The sensecap works out of the box, the above link has the video of it. You need flux 1000 collateral to mine. 

Paid about 500 nzd including shipping, looking for $350. You can use it as a general PC if required.