Question What GPU should I get under £100 or should I save up for something more expensive?

[KKEGAMING]

I currently have a pc including
APU: Ryzen 5 3400g
RAM: 2x8GB 2666mhz
MB: Gigabyte GA-A320M-H (Rev 2, I think)
PSU: Cooler Master MWE 500 230V

Is there a GPU could be recommended under £100 or is there no point upgrading at that price point? Also if recommended where should I look online for it? Thanks for any help, I'm pretty new to any of this.

 

[--SID--]

2nd hand GTX 1660 Super/1070/1080.