Don't misunderstand. We're not explicitly saying you can't outline. We're saying, don't think of it as such. The black color can be used to define shadow very well, if you use it and apply as a shadow instead of "oh, i have to outline every single piece of him" No, just think about how light is hitting him.
Also, you're not using all 16x16 space. Why not? Also, it would probably look better if his legs weren't so stretched apart. It would help to look at some other 16x16 sprites for ideas. One thing they tend to do is make big heads.
I would keep working at this resolution. There is much to learn about pixel art here.