What GPU would you pair with an i7 4790k without being ba ridiculous mismatch?

I helped someone build 2 PCs for themself and their spouse, and in return they gave me some spare parts they had lying around.

Those spare parts ended up including an i7 4790k, motherboard, and RAM.

i understand it’s not 2014 anymore and that CPU is old right now, but I’d like to turn it into a modest gaming machine and give/sell it to someone as a cheap first gaming desktop.

I’m in the US. My first thought was something like a 1070, or an RX 580, but looking around Offerup there’s also a few 1660s and 5600 XTs for cheap as well.

Looking for ideas for 1080p gaming. Ideally something that will be slightly bottlenecked by the CPU/RAM so that when the buyer upgrades the CPU/RAM/MB the GPU will still be relevant.