What is Octoprint?
Octoprint is a program that runs on a linux computer and manages a printer. It gives your printer a web page. You can look at the printer - if you have a webcam you can get a timelapse of your print, you can even see where in the print you are.
You connect your printer to your computer running Linux. When you want to print, you transfer the file to that computer with the octoprint web interface. Just drag and drop.
Then you tell octoprint to read the file and transfer it to the printer, bit by bit. If you are willing to accept the security risk, you can open a port - or set up a vpn and check the progress of your printer from your smartphone.
So what do you need?
You need a computer to run Linux. This can be an old computer but you can also run it on a Raspberry Pi, like this one https://www.amazon.com/gp/product/B01CD5VC92 - this new model has built in wi-fi. You can save a little money if you use wired ethernet, but this one is better if you just want to put it somewhere and use it. You will need a memory chip and a power supply and a case...I think it is best to get something like this kit https://www.amazon.com/gp/product/B01M65MPRE and, as you see, this case has different versions that contain different stuff.
You need the power supply, the case, the SD card. If you have any problems, you will need a HDMI display (like a TV), an HDMI cable and a keyboard. I got the $33 kit that had everything.
Running Octoprint on the Pi is very common. There is a complete software installation kit that includes Linux and everything you need for octoprint at http://octoprint.org/download/ and all the instructions you should need are there.
So, again, this is a wiki. Feel free to revise and extend my remarks. I really can't do it alone.