First, I love the fact that you did a birthday present for your friend. If anything it only makes it harder to judge because everyone knows you only had the best intentions at heart when making this.
When staring at this piece I immediately was brought back to how I originally did art (and still do when I'm being really lazy). It's a bit chaotic and overly blurred to give the effect of texture and it's just not working too much for this picture.
I do enjoy your attempt at trying to add the fluffy fur appearance to the character. It's something I always immensely enjoy when studying pictures.
The eyes could use some more definition. A pupil, or a bit more direction of what you were trying to create here. Don't get me wrong, I love when people use a multitude of shadings to create a realistic and colorful eye but it's just lacking the shine and realistic look of an eye.
The text is whimsical and I can tell you did that by hand/mouse. Very cute!
My best suggestion would be to study up on anatomy and go to some livestreams or join.me sessions by other artists. That, and layers can be your best friend for doing unique effects and different coloring styles without taking away from sharp, detailed lines and other effects being wrongly blended together.
Whatever you do, don't stop trying. Keep doing art and you'll only continue to improve!