leemajors had a good post above recommending prebuilts. Duh I completely forgot that since for so long building your own system was a far better solution. But today it's not so bad. I saw a CyberpowerPC system on amazon for $800 that has a last gen i5, AMD RX 580, and 8GB DDR4 RAM with a 1TB HDD and a legit Windows license for $800. My build I posted above was assuming you'd pirate Windows.
I think RGB lighting is ugly as , but this ain't bad for $780.
https://www.amazon.com/CYBERPOWERPC-.../dp/B0747W15QL
EDIT: Crap, I forgot you already bought a case