Hey, welcome to your first game jam! This game jam that first came out 3 years ago was one of my first ones too! I like this game as it gets more difficult and you have to rely on your money to last more and more waves. It has very simple and tiny graphics but it's very cute to look at.
Now for my suggestions! The player moves faster than the bullets, which I found weird. I also think there should be a reload sound effect to let the player know they're reloading and when it's finished reloading. Also, repairing the barricade that's already destroyed shouldn't use your money, since accidentally pressing that with no benefit will cost you the game.
I have a lot of fun doing game jams and I hope to see you doing some more too!