Building a CHEAP Hack server. Need parts suggestions.

I already have an SSD for macOS, and some internal HDDs for big storage, but I'm wondering what type of CPU and Mobo I should get.

I want to spend less than $150 on a CPU, Mobo, RAM, Case and Power Supply. Suggestions?

This server will only be used really for hosting data through Plex, maybe other small tasks, but I don't need anything crazy.