Answer: you want r/PMsForSale + FindBullionDeals.com

Make sure you read the sidebar on Pmsforsale, they have rules and a flair system in place to prevent scams. If you follow their advice, you'll likely never have a problem buying or selling. If you have patience and check it regularly, you can find plenty of spot and even below spot deals.

Findbullionprices.com meanwhile covers every major reputable vendor, from JM Bullion to Liberty to Monument to BE. Real time pricing too. You simply won't and can't find a better source.

There really are no better answers, you can safely ignore pretty much all other advice (edit: except Costco when you get the right deal with the credit card cashback).

If you are looking for high-end collectibles, I am the lowest price online - I'll lose money before being undercut by any reputable vendor. Mydnight.com for easy Linktree, show links and reviews.

If you are looking for custom work, you want u/GlassPanther or u/TDMetals - both extremely trustworthy individuals with stunning work and premiums lower than pretty much every other decent silversmith.