For your first piece, it truly is quite decent. Good job. 

Here's a link of essentials that should help you on your way~

http://cyangmou.deviantart.com/art/5-Tips-for-the-Aspiring-Pixel-Artist-457660938

Funnily enough, the most recent version on my computer has the shadow between her jacket and her shirt. I just uploaded before I added it. 

I mean the right side of the piece, not the adventurer. Just to show the shadow the jacket may cast on the shirt on the gap between them. As a subtle detail.

I don't want to sound fulsome, but that's great as a first original pixel piece, and you don't suck at all. Even if it's not perfect you may have got remarkable potencial, so if you have the time, even if it's a final version and not a wip, this piece may deserve a revision.

I struggle with faces so much. :P Decided to keep it simple for now and work on the face later. Go simple now instead of awkward and creepy. It'll be adjusted accordingly when I suck less and I'll throw in a background or more characters later. :)

Her chin was the target of a fair amount of reshaping, in the end, this is what I went with. She either looked skeletal or fat. Not sure how to fight that... Maybe it's the angle of the head? Maybe it needs actual shading... I dunno.

Also, right side of the picture or her right side? 

wow, your first original pixel piece?

Very very nice! I really like it.

To my taste I think her chin looks a little manly (but depends on the model you want for your adventurer, not all of them should look like Mrs. Croft.). Maybe the right side of the shirt would thank a little shading, and the mouth less simple?