This was my first game jam as well.. I've done partial games before but never got a full completed experience. I can't really talk from experience but what I would say is there are a couple of things to really focus on
1) Sound! sounds are so vital to a game and can really be the make or break difference. Everything from background music/ sounds to menu interactionsA
2) In the same vein as sound you need to add "juice" to the game. What that means is interacting with the character and the world needs to feel impactful.. You can do this through things like sound but also visual effects that indicate an interaction takes place. Finding the right sounds completely changes the game.
This is the game my friend and I made. It's pretty amateur as well, but I tried to do some of what I talk about... Its not perfect and I have a long way to go The Hamster Engine by ADKeiber, ThisGuyCaleb