Hasn't been updated since 2020, but Tim Dettmer's guide [0] is pretty much the gold standard for optimizing what to buy for which area of DL/ML you're interested in. The pricing has changed thanks to GPU prices coming back down to earth a bit, but what to look out/how much ram you need for which task hasn't. Check out the "TL;DR advice" section then scroll back up for detail info on why and common misconceptions. For the tips on a RAID/NAS setup alongside it, just head to the datahoarders subreddit and their FAQ.

[0] https://timdettmers.com/2020/09/07/which-gpu-for-deep-learni...