You have a decent start with the processor.
The power supply is going to be your limiter for the graphics card.
If you look at the power leads available out of the power supply, I doubt that you will find a 6 pin aux pcie power lead.
About the strongest card that will run without extra power will be a GTX1650. That is a good upgrade for gaming.
Perhaps something like this:
https://www.newegg.com/evga-geforce-gtx-1650-04g-p4-1151-kr/p/1FT-001K-004V9
8gb of ram can be restrictive so a 2 x 8gb DDR4 kit might be $60
For the future, try to replace a windows HDD C drive with a ssd.