Spinels, velvet blues, and emeralds you should always sell right away.

Should you sell spinels in re4?

You are safe to sell them as you find them because they don't appreciate in value (besides the dirty items that can only depreciate in value).

Should I sell all valuables in Resident Evil village?

In terms of what we'd recommend selling, you should sell anything that's classed as 'Valuable' only. You should see that under the item's description in the Duke Purse section of the shop, as you can see below. Valuables have no other use other than being worth money. You can sell them without any worry.