Building a gaming pc is easy if not going with a custom water cooling loop. I’d say you are best to do it yourself, the skills you learn will serve you well when it comes to upgrading or fixing issues when hardware fails.
I am all for supporting local business but unless you really cannot build yourself I would recommend it, the knowledge gained is very valuable.
I didn’t build a whole system but I was swapping parts when I was about 13, it’s not hard.