Confused about whether to buy a CPU or GPU

Hey!

My current specs: i3 3220 Intel DH61BF 4GB 1333MHz DDR3 Kingston 240GB SSD

I followed the vanilla guide and managed to install Mojave on the PC, but then realised that the iGPU ( HD2500 ) is not supported in macOS. So no hardware acceleration and I'm stuck at 1024*768 and that looks terrible. So I see two options in front of me, either get a CPU whose iGPU is supported, or buy a GPU.

I was considering the i5 3570K which I can used for about $85. Would it be ok to run this on a stock cooler?

For the GPU, I wanted something that worked OOB and was cheap. I can get a RX570 used for about $115. Which should I get? Or is there a cheaper option I could try?

The PC isn't going to be used for any resource intensive stuff, building a hackintosh is just something I wanted to try 😅 Tried using whatever hardware I have around.