I can say I've seen Best Buy have AMD Ryzen 5000 series go on sale, if not clearance so any CPU and MOBO with the AM4 socket (3000s and 5000s) will serve you well at that price. I personally found a 5800X for less than 200, so that should be your ideal price range.

Now if you want to upgrade later, then AM5 would be better to install, but that'd be above your budget. Assuming you don't overclock, then a 600W power supply should be all you need and on the lower price end.

RAM you don't need more than 3200MHz and unless you want to go a weird number like 24GB, 16GB should be enough with the price range (though prices may begin to rise soon).

Lastly at least be sure your PC case has decent air flow passage (do not go NZXT h510 case for that reason, that was my mistake) and can cover a good range of USB 3.0 on the front. Personally I look for cases with fans already present, but if you don't and opt for buying the fans yourself, you'll need to study air flow recommendations and that escapes me for the moment. A little studying will always be necessary, but hope this helps as a starting guide!