Can confirm that's actually legit Microsoft Support via chat. Connected to them a few times in the past.
During the past two years they've actually made it harder to contact an actual person. And most of the numbers you see online do advise you to use Get Help or it's web version: https://support.microsoft.com/en-us/home/contact?SourceApp=smc2&ContactUsExperienceEntryPointAssetId=S.HP.SMC-HOME
You have to be filtered through this Get Help app or link. You need a Microsoft account for this to work.
I'll hazard a guess they sent or provided you a service request number.
Might want to edit your first post and include vital information like hard drive, power supply, cooling, etc., etc. Those would factor in on what people here will recommend.
Also what games are you planning?
Use the Cheap Dell Gaminc PC guides floating all over the net minus the video card. Spend the money for the video card on hard drive instead.
https://www.youtube.com/watch?v=jxHiwq7QqJc
https://www.youtube.com/watch?v=o8BIWIPBt18
Depends on how much you're willing to spend. If your parents already have a monitor and other peripherals already you might want to go with the Dell Optiplex Gaming PC route.
https://www.youtube.com/watch?v=jxHiwq7QqJc
https://www.youtube.com/watch?v=o8BIWIPBt18