As someone that has been participating in game jams for almost 8 years, the best piece of advice I can give you is to set a goal for the event, What do you want to get from this? Some people want to learn something new or improve a certain ability, some want to meet new people with the same interests, and so on, don't focus too much on the game part, I know that sounds weird, but in my experience, the game is never a problem.
Remember that if you want the free course you don't need a fully fleshed out game, just a playable demo, check my profile, I have three games I made during different game jams: Rabbits VS Veggies, Twilight Gal, and Gaze, try them out, see if any of them feel complete, spoiler alert, not a single one them does.