The idea itself is very cute, and it looks really nice. However, I do think you could do better with your outlines and coloring. It does look a bit messy, which isn't a bad thing, but if you cleaned up your drawings, they would look a lot better.
I recommend using an outlining pen of sorts to do your outlines. Here's what I do- sketch proportions with pencil, draw a rough outline with pencil, go over the outline with the outlining pen, then (after the ink dries, I usually wait a minute or so) erase the pencil. If you don't have access to any high-quality outlining pens (I use Staedtler), super-fine tip Sharpies will do nicely.
Also, another tip- experiment with shading. If you really put time and effort into shading, it will come out much better. Look at other artists' drawings to see how they do their shading, and how the light affects the shadows. I learned a lot this way, and I know it can help you too, if you practice!
As for your proportions with the Charmander itself, it's looking really good. The only things I see really wrong with it is that its wrists are a bit too thin, and the pose looks uncomfortable with it sitting on its tail. If you were to redraw this (I'm not saying you have to), I'd recommend putting the tail to the side of its body and having it curl around so the tip is in front. Sure, it'd be different, but less unnatural (at least in my opinion).
I hope these tips helped, and happy drawing! =D