When to use double negatives?

I know in Spanish it’s very common to use double negatives, and is in fact considered grammatically correct, but when are they used? Because I’ve seen sentences that use words like “nadie” but don’t use double negatives, while other sentences such as “no tengo ninguno” use them. Sorry if this is kind of a vague question, I’m just very confused >.< thank you so much!

submitted by /u/IlGufoScuro
[link] [comments]