I am new as well and have never successfully finished a jam and I think that was due to overscope so I would say try and keep it to a smallish size personally I am going to be making a arcade style game
Definitely manage your scope. I usually implement 2 or 3 mechanics and leave time to build levels and test! Use free assets/resources to make your life easier especially if you're running out of time (for things like music etc)
