Don't over scope your project if you want to finish it for the jam. Scope is probably one of the most difficult things to limit for new game devs/jammers. You should try to complete a single level or a single vertical slice of the game then polish it up.  Take whatever idea you have and write down the core mechanics for it then put anything else into a document that you can call "Stretch Goals." 

You can also try to join a team with other people who have done jams before and that will let you learn a lot about it.

I recommend you make something you're 100% sure you can finish because polishing what you've made is also very important and I can tell you by my own experience that it can make your game much better.