Write down three things: the games you (or your kid) actually play, the resolution of the monitor you have, and a budget that will not keep you up at night. Leave RGB and “future-proof forever” for later.
Ask what ready to play means. You want Windows activated, basic updates done, a real stress test, and a contact if something fails. A long specs list on its own is not a good purchase.
Use Find my PC or a path on the site to shortlist what is listed, then message. A local seller who explains trade-offs in plain English usually beats the cheapest anonymous listing.
Plan the day after. Who do you call if a drive fails? That answer is often worth more than another few percent of GPU performance.
Not sure what you need?
Pick a path, run Find my PC, or message with your games and budget. We will keep it practical.