There's heaps of stuff I could list, but you're better off watching some youtube videos for that. The best piece of advice I could give is to make sure you make a complete game, working on every aspect of the game equally, and not missing out on an important part. I've seen too many games that had great game mechanics and art, but were missing sound effects, or had bad controls.
I think you did well for your first game jam, keep it up and you'll be making some amazing games.