Well I think at this point you need to first see the condition of the item when you get it. If it is only faulty, then you really don't have any case at all. If you get something that is quite clearly not in new condition, clearly having been used, then you should have a case with eBay, so long as Banggood will provide you with a letter confirming a new item had been sent.
You will really need to see what the condion is before you decide what to do. Getting a full refund has to be an option, but then you will end up paying shipping to return it. That may not be worth it, it might work out better to get the new gimble and then re=sell it again, but then it will be second hand and not worth as much.
So you'll have to work out what the best option is to do.