In my opinion the best options for gem choices are support the author and bonus scenes. I don’t like the “extra outfits” one because there’s usually nothing special on them. For example, on the episode official stories, you can pay gems for special and unique outfits but what’s the fun if the outfit is normal? Also the thing about adding gem options for outfits and choices, is that it’s an episode official story 2.0 which is what people don’t want. I don’t read episode originals because of that and I won’t read a community story with that as well, gems aren’t that easy to get.
As to why I think those three options I mentioned before are the best ones for gem choices, basically for bonus scenes is something in my opinion it’s worthy to spend gems on. I love reading different POV’s and stuff so I don’t mind using maybe 5-8 gems to read one.
Then support the author it’s nice because it’s a way of spending gems when you can and that it won’t affect your experience on the story. Sometimes I don’t have gems and if I see a story with gem choices or other gem related things in the middle of the story, it’s frustratig. However, if I don’t have gems and there is support the author, I have the option to support the author later on once I have enough gems.