i made it by following a tutorial and i modify it by my own design
This is not horrible as your first attempt. I've seen much worse.
You should just try to avoid those bad poles and ngons. 5x poles and ngons are acceptable (and unavoidable in most cases), but more is just bad modeling. The polycount is quite good and subsurfaces are used well enough. Personally I would avoid to use multi-layer characters for animation (I mean body and dress). But having more layers could be good as a base to build more characters.
I can't understand why people keep using Blender layers to separate objetcs. This is a nonsense. Layers in Blender are done for scene visibility and not to separate the character objects. You can use the Outliner for that. For a single character just use two layers, one for the mesh and another for the armature.
She looks more like an uptown girl than a witch ,nice piece.