Yeah stay away from r/gaming haha. I've had the most success with r/Games, r/creepygaming, and r/ARG, although obviously it depends what kind of games you make. The way subreddits prevent users with low karma from posting is annoying, but i think if you drop some memes in r/funny or something you can build karma pretty quickly. Or, yknow, actually participate in subreddits like r/gamedev. Shadow banning is annoying but Reddit gets a lot of bot traffic so over the years they've had to implement lots of anti-spam measures; that's one of them.
I don't want to deny anyone else's experience, I'm just noting that, for me, posting on Reddit has been by far the most effective free marketing I've tried (actually it's been more effective than most of my paid stuff as well). I don't want people to be scared away from trying it altogether because it might be really helpful for them. Or it might not. You don't know until you try.