Great job with this being your first game! It has charm and is a good base for you to build on to. Here are a few suggestions that help juice up the game feel. This things should come after you get the core gameplay polished, but it can often be overlooked and adds a lot to the game:
- As Toby mentioned below, Coyote Time is really beneficial for platforms. Both 2D and 3D. Definitely look into it and it'll make the gameplay more forgiving and fair
- If you want the jump to have a bit more air time, look into adding a slight hover when the jump is at its apex height. This is more of a personal game-feel suggestion, but I find it works great!
- Giving the player sprite some squish and bounce when it lands and jumps will add a lot of juice to the movement.
- Some little particle effects when the player does an action (run, jump, land) also helps juice things up. A little poof trail while they run goes a long way!
These are just some suggestions that are less about gameplay and more about how the game feels when you play. Hopefully it helps with this project or the next, but great work on this and keep it up!