For some things, you don't need outlines at all. For example, the golden trim on the shirt would leave you more room for shading and detail if you left it without outlines, since the yellow contrasts well enough from the dark green.

Where is your light source? Different parts of the character appear to be lit from all different directions. When adding shadows, choose where your main light source is, and put shadows where light from that light source can't reach. It's a lot easier to make good-looking shadows if you think logically about them.

I know the line on her neck is meant to show off the way her neck is positioned, but it constrasts way too much with the skin color. Either use the skin-shading color for that line or get rid of the line altogether for a better look. If you get rid of the line, shade part of the shoulder that sits to the (viewer's) right of her neck to help make the shape of her neck "pop" in contrast. (Even one three-pixel "L" cluster of shade right next to that one-pixel curve in the outline could do wonders in that regard.)

Also, an important thing to ask yourself about outlines of any kind is this: "Do I need them for detail/readability?" Try getting rid of any outlines that separate one part of the body/clothes from another (e.g., the outline on her face) and either shade appropriately or use anti-aliasing. "Internal outlines" such as the nose line and the cleavage line can stay, but consider how contrasting they need to be for them to work with the rest of the piece. (In re: the cleavage line, consider whether you can get away with simple shading on the line itself and a tiny bit of darker shading in the "gap" at the top of the cleavage.)

The base work itself shows promise. You have a good grasp of anatomy here, and while the shading could use a little work, you obviously have a sense of knowing how light and shading works in general. Keep tweaking your work and you'll have something really good on your hands.