Step 1: Obtain the fastest, yet cheapest, computer you can find.
Step 2: Load your server software.
Step 3: Config software.
Step 4: ???
Step 5: Profit!

Nah I’m just messing with you…

Ok, So on ebay people are selling loads of used PCs for less than one-quarter the retail value. i3 and i5 machines going for less than $300 USD. I managed to find one for $140 inc. shipping, your millage will vary. Some need additional hardware, some are complete machines lacking an OS. My machine is a Dell Optiplex 390 with an i5-2400, 8GB DDR3 RAM, 500GB Seagate HDD that was wiped by the seller. Good little machine, plenty powerful for my needs. I run Plex and a VM to play in on it with plenty of resources to spare. It’s quiet and cheap when compared to new hardware. I added a 4TB HDD for plex but that’s not important.

I needn’t to explain how to install Linux and the associated programs but it’s easy to find on the webs. On the server, I split the primary drive into 3 partitions, one small one for the OS and two 64GB partitions for the plex library and /home. Some of the software includes, apache+php for a file manager to dump files when I want to, plex, resilio sync, and virtualbox. My webdev VM runs Ubuntu Server for various web stuff. I think I did good. :)

Parts List:
1x USED PC (Dell Optiplex 390 MT = $140) 1x Extra HDD Caddy = $6
1x SATA Cable w/ right angle connector = $4
1x 4TB WD Purple Drive = $135
Total: $285

Potential upgrades include a SSD for the OS and some data and maybe some more RAM.

Note to potential buyers: This Dell computer is not compatible with VMware ESXI 6.5 and probably older versions without adding networking and storage drivers. I couldn’t get to the point of installing it so someone out there might know how to succeed. Leave a note in the comments if you do. I opted for xUbuntu and virtualbox for my WebDev VM. It works, can’t really complain.