I think that's very sound advice from Gordon, welcome to both of you to the forum btw
Research is king in this business.
You have to bare in mind that just because a product might sell well world wide, the question needs to be can you compete with the sellers?
Remember, eBay isn't an even playing field. You have big time sellers buying in massive volume and selling at a reduced margins to get sales and dominate the market on hot selling items. So knowing that the product they are selling might be a hot seller worldwide is of little use to you if you can't compete on the same scale that they are.