how to do in-game currency for online games on steam?

Not talking about micro-transactions. I'd like to know the proper way to have a number linked to your account like for example XP, currency, stats, etc. Should I just use the standard save system and not bother with steam at all? Could it be possible to cheat if that value is stored on the unreal save file? I have no idea where to start with that one to be honest.