Budget $600 1080p gaming PC: CPU vs GPU and new vs used

[HarperCH]

I'm trying to put together a budget gaming PC build for around six hundred dollars, aiming for solid 1080p performance in current titles without needing to upgrade for a couple of years. I've been researching parts, but I'm getting overwhelmed by the trade-offs, like whether to prioritize a better CPU or GPU with such a tight budget, and if used components from the last generation are a smarter risk than new entry-level ones. For builders who have recently completed a similar project, what was your component selection strategy and where did you decide to splurge versus save? How did you navigate the compatibility between older motherboards and newer CPUs, and are there any specific retailers or times of year you found offered the best value for key parts like graphics cards and power supplies?