Sell them at your peril. I have known many a relationship destroyed by someone selling an item that was GIVEN to them. Some will argue it's OK, because the item now belongs to that person, but there are a lot of grey areas IMO.
Last summer, a colleague of mine bought her niece (aged 15) a specific item from Disneyland Paris - from a Disney film she loves. Cost some €100 euros, so around £86, and her niece was delighted with it. Put pics on twitter, facebook, and instagram of herself with said item.
Then 3 or 4 months later, her sister in law (niece's mother) said their neighbour from 3 doors down had a little girl aged 5 who had popped around for a coffee, and the little girl 'fell in love' with the item. They didn't have the heart to take it off her, so they gave it to her. (With the niece's agreement of course.)
Rightly or wrongly, my colleague was fuming, and they haven't spoken since. She said she was furious that this frankly expensive and special collectible toy (that she lovingly hunted down for many hours, and bought for her niece from PARIS,) had been thrown away to a random neighbour. She said to her SIL that she will NEVER buy any of her children anything again. And as I said, they've not spoken since. (My colleague's husband hasn't spoken to her or his brother either as he was pissed off too.) This was November time, so some 7 months ago.
So yeah, be careful @SkyIsBlue55 If you ARE going to sell stuff GIVEN to you, (or even give it away,) consult the person who gave it to you.