This reminds me a lot of my own work from a few years ago. You're well on your way; you just need to keep practicing and keep churning out work. I really like your pose, the outfit design, the facial expression - it's all very playful and gives a good idea of this character's personality.

For now, I would suggest to work on your shading. Make your darks dark and your lights light. But more importantly, don't be afraid to use different colors when you're shading something. For example, you've shaded your greens with a darker green, but have you ever tried shading it with a darker red instead? Using a different color can make it feel more "alive". Using the opposite color generally works well - you don't have to go overboard, but a little bit brings a lot more depth.