Gaining experience should be the number one priority before you start on a game. Do read up on Roblox’s Documentation or on already-existing topics on the DevForum. Try and make sure not to use YouTube tutorials, as some Developers would find themselves in what they call Tutorial hell if they overly rely on tutorials.
A game idea would be an obby. Everyone has to start somewhere, but instead of making your typical obby with countless stages and resistive obstacles, try to include new obstacles when a certain number of stages are completed. Try to place different challenges for some stages (for e.g, you have to complete a certain stage within a given number of time, or you fail).
Well, I couldn’t say what content that majority of the Players enjoy. The best thing to do if you’re unsure of whether your game is repetitive/has too little content, is to collect feedback. You can do so by opening a topic under #help-and-feedback:creations-feedback to ask fellow Developers to test your games, or simply ask your friends.
Thank you so MUCH! This really cleared my mind from the overthinking stage of when it comes to games. You were able to explain on what I should rely on, and what to do.