Listing things on Gumtree is definitely not working out - I have had less time wasting nonsense which I guess is a plus, but that's because I have had no enquiries at all (apart from the initial two scam messages which were so quick I presume were bots).
It changes over time too. I used to be able to list pretty much anything on eBay and have it sell, now stuff just sits there (and there is not the volume of buyers to allow you to do the auctions any more either). Marketplace was ok-ish, but these days people don't seem to know how to communicate and mostly just waste time - and you and up wasting other people's time because you are so swamped with the dodgy people it is really hard to keep on top of messages.