You pretty much sums all the scams revolving around the game. There's one thing I'd like to add which is for those people selling their cards thru outside source (facebook, discord etc.) Just stick to the marketplace and legit third party markets, it's more safe.
ign: deathfool
Agreed, thanks for the comment. I mention this in section 2, that for any trade or sale you have ALWAYS SUGGEST USING A LEGITMATE PLATFORM or sell using the IN GAME marketplaces. If their intention was to scam you they will act very offended and proceed to "Take their amazing deal" elsewhere. Welcome to the giveaway and goodluck