Here are the parts for the $300 gaming PC build that I did.
Total Price: $298.97

Featured
SP 512GB SSD w/ SLC Cache
SP 512GB SSD w/ SLC Cache

Retail - $43.99

Bought For - $43.99 on Dec 13, 2021

ASUS RX 550 4GB
ASUS RX 550 4GB

Retail: $125-$175

Bought for: $124.99 on Dec 13, 2021

Dell Optiplex 9020 MT - Core i5, 8GB RAM, 500GB HDD
Dell Optiplex 9020 MT - Core i5, 8GB RAM, 500GB HDD

Retail: $129-180

Bought For: $129.99 on Dec 13, 2021

Budget parts to make it a full system