Today I'd like to recommend a choose-your-own-adventure series that I really like: d20 Pony. It's a long running series, in an expanded universe based on MLP G4, but with new areas to explore and species to meet. It's a really fun and exciting story with epic adventures and very likable characters (especially the main two: Trailblazer and Moonflower). It's mostly based on OCs, but there are also some canon character appearances.

It works like this: anyone can post a command saying what the protagonists should do next, then one of the commands is chosen at random and executed, and the next part of the story is revealed, together with a 16-bit style picture. Sometimes there are dice rolls, used to determine if an action succeeds or not (hence the name). As you can see with the current entry, I'm taking part in it too (I'm "nopony" there). It was a part of my inspiration for the "Champions of Celestia" roleplay (the other part are my Tails of Equestria sessions, hosted by @abrony-mouse).

Even if you're not going to take part in it, I highly recommend that you read it from the beginning, and treat it as an illustrated fanfic. (Warning: Sometimes it gets a bit adult-themed. It's nothing explicit though, just things like a vague description of the situation.)