Raspberry Pi 3 (both my setups use these I don't know if any older will suffice), microSD in it with
DreamPi installed
USB modem, line voltage inducer. I strongly recommend
these as they're combined into a single clean plug. Be on the lookout for when it's stocked
EDIT: Right now looks like can order the full kit rather, a good c-note to spend, to be sure I saved a lil when I bought my Pis I got them from Amazon $50 a pop but I'm afraid prices are jacked up cuz the chip shortage