eBay does have a good money back guarantee, but you still want to avoid having to use it if the listing is an obvious scam. Scammers know how the rules work better than the average user, and there are things that scammers can do to make it harder for users to get their money back.
It is much better to avoid a scam entirely than to have to work to get a refund.
In general, you can avoid a lot of headaches by choosing to purchase only from established sellers that have recent and past positive feedback as a seller for selling items in the same category that you intend to buy. If someone is selling a dozen apple watches, but has no feedback, or only has feedback as a buyer, or only has feedback for selling dress patterns or fishing lures (actual examples I have seen), perhaps wait until they have a track record of positive feedback for selling electronics before you buy from them.
You might miss out on a good deal from a new seller once in a while, and nothing can guarantee that you won't still run into an issue anyway, but you can avoid a lot of potential problems by choosing to do business with established sellers. Anyone can put together a listing that looks nice -- it is not hard at all to simply copy an existing listing -- but it is much harder to create a history of consistent sales and positive feedback.
For more experienced sellers, you can learn a lot about the sort of seller you are dealing with by checking the seller's feedback page to see where the seller is registered and to notice if the seller has any negative feedback. If you see negatives indicated in the table of recent feedback, you can choose to exclusively see each type of comment by clicking on the numbers shown in the table. Reading negative or neutral comments can often tell you if a seller has a pattern of problems with items not matching the descriptions, canceled orders, late deliveries or item location misrepresentation.
If a seller has a pattern of too many serious negatives -- or just not enough positive history -- it is often better to find another seller with a better track record to do business with.
