Ok I'm back here

First ur prebuilt ur gonna base this off is an Optiplex 3020.

https://www.ebay.com/itm/Dell-Optiplex-3020-Mini-tower-desktop-computer-i3-4160-3-60GHz-4GB-500GB-Win-7/163927931882?epid=1739676225&hash=item262addbbea%3Ag%3AVuoAAOSwe0xdvbDt&LH_BIN=1

40 USD.

Next, 2 x 4 gb ddr3 ram.

https://www.ebay.com/itm/A-Tech-8GB-2-x-4GB-PC3-12800-Desktop-DDR3-1600-MHz-DIMM-240-pin-Memory-RAM-4G-8G/221892835721?epid=18035164180&_trkparms=ispr%3D1&hash=item33a9d7f989:g:T60AAOSw9J9dxeC~

21.99 USD.

An ssd for faster boot times (not necessary, but improves quality of life and it'll make this seem way faster) 120gb, use this for Minecraft and your Operating system.

https://www.amazon.com/Kingston-120GB-Solid-SA400S37-120G/dp/B01N6JQS8C/ref=mp_s_a_1_1?keywords=sata+ssd&qid=1575227301&smid=ATVPDKIKX0DER&sr=8-1

18.69 USD.

(You might need a sata cable to connect it) https://www.amazon.com/BENFEI-Straight-Locking-Compatible-Driver/dp/B07CWQDPG7/ref=mp_s_a_1_1_sspa?keywords=sata+cable&qid=1575227362&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyTFNNQVhDSlNGRlNQJmVuY3J5cHRlZElkPUEwNTE5MDkzUUNBWUJTWjhYRFJXJmVuY3J5cHRlZEFkSWQ9QTAzMDM3ODFaQk9HWkxXMFRQNk0md2lkZ2V0TmFtZT1zcF9waG9uZV9zZWFyY2hfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

5.85 USD (if u can find cheaper take it)

Graphics card is a gt 1030. https://www.ebay.com/itm/Gigabyte-GeForce-GT-1030-OC-2GB-Graphics-Card-14210/264506702404?hash=item3d95d3fa44%3Ag%3AePEAAOSwcdtdrjAF&LH_BIN=1

65 USD.

~ 156.83, not including shipping.

Edit: swapped out 1030 for different one, because the DDR4 ONE STINKS and I accidentally let it in