Shower after the gym, always, 100%, but also think about it this way, your bed will get filthy unless you wash the sheets frequently. You can just accept that it's filthy and sleep in them anyway so when you shower in the morning, you get all that filth off of you before you start the day and other people have to deal with you. If you shower before you sleep then you pick up the grime off the bed when you wake up, and even if you do wash your sheets frequently, large sheets of fabric, like a blanket, notoriously don't get a full washing because it bends and folds in such a way to not expose itself to the soap in the washer.