You could try Etsy for any items that are either vintage or at least 20 years old. 

There are some specific platforms for selling clothes, like Poshmark.

You might want to google search for the best ones - I've only heard of Poshmark (they recently expanded to Australia), but I'm sure there are others.

However, this does not mean you won't get scammed, especially on high priced items.

Another option might be for your local FB marketplace.