This is so hard for me to answer. I’ve decided that it takes me on average, 15 hours to create a 15 minute episode. But there’s so many external factors that change that. Like am I motivated enough? Do I have free time? Am I doing a lot of branching or advanced directing? Do I need BG characters? Do I need outfits? Etc. Like, I know I’m capable of writing an episode in a couple of days but I’ve also taken a month just to finish one episode too.
I have one with over 30 episodes (ongoing), one with three (completed), two with four (ongoing)
This totally depends on your story and your goal. If you want to trend, as often as possible. If your story covers some serious topics, I also recommend as often as possible because some cliff hangers just shouldn’t be left hanging 
Without knowing what your story is about, I’d say updating once a month is pretty reasonable. It’s not too long that people will forget about your story, but long enough to make readers go “I’m so excited to see you updated today” because they probably weren’t expecting it