Spark
Broken
Well, I usually buy from the lowest seller, but make sure they've sold a lot, it shows next to their name how many they've sold. If it's over 1000 you're usually good.Wowzers - can you only buy from sellers in Britain or can you go for the cheapest?
Also make sure the key you're buying is for steam/origin(depending on which game) and is for your location(Global).