To be honest, the quality is far from the standard on GraphicRiver, plus you’re using a copyrighted character which you’re trying to sell on your own, which is actually illegal.
hi u have start with reworking the shadowing this is either missing or being inappropriately done , as yours, at this stage is following no real logics indeed . the global style is a bit too childish and made of basic shapes almost exclusively and here is “where the big dogs play” and u are expected far more than this indeed. The illustration style and colors are too flat, introduce some gradients , use more complex shapes using the pathfinder and so on … introduce all shadowing where required, like in the ears , with the mesh tool or gradient tool at least, these sort of things … it would be also welcome to have a stroke around the different shape to adapt to more trendy styles too