If you have a Microcenter near you, stop in and chat with the guys in the back. There's one in Paterson. Sometimes I go there just to walk around. It's awesome. They pretty much all know what they're talking about. They sell pre-built, or you can literally talk through all the parts and then pay them to build it for you.
Online pre-builts are fine, but there's always stories of damage in shipping, etc. May need some assembly on arrival if you're not comfortable with that. On top of that, they sometimes cheap out on some stuff as the primary selling point is the CPU/GPU, but then they'll throw in an ugly motherboard, cheapo RAM, low quality PSU, etc.
A lot depends on what games they want to play and at what level. I've built pretty much every computer I've ever had, and watercooled most of them, but I do it for fun. Don't really have much time these days for games. Current build is maybe 2 years old and watercooled. Ryzen 5600X CPU, 6600XT GPU. Those are the parts where most of your money will go. RAM and NVMe drives are cheap, so go for 32GB and 2TB respectively. My current build is overkill for regular users, and somewhere in the middle for gaming. You won't be playing brand new titles at Ultra graphics and 4k, but it will still handle them fine at lower levels, plus like 95% of other games.
