I sell my cards on eBay and I like to think I'm legit :)

Seriously though, best advice I can give is just to always check their feedback history before purchase. Photocard buyers are an unforgiving lot so everything is inspected in ultra detail. I don't really collect cards myself so sell the ones I get from random album buys.

I sold a Dreamcatcher 1st Album photocard stored in a toploader, then a do not bend envelope, contained in bubble wrap housed in a small box sent via tracked delivery. Overkill maybe but I know these are important to someone.

Because it was such an expensive card I even put a public photo of how it was going to be shipped on display on the eBay listing to be sure they were happy before purchase. Had some glowing feedback when it arrived as I even sold at 50% below market rate by default to avoid international sales.

Then I sent someone else a regular card in plastic sleeve, a plastic sealed bag for rain protection and do not bend envelope complete with freebies and had a comment they expected more from me. That was a bit upsetting.