Hello! I made you a quick edit.
First of all, you should work smaller. This way you can concentrate more on the pixels themselves, and experiment with Anti-aliasing. If you outline things, try to outline everything, and adjust the color of the outline according to the lighting. This is because you don't have so much space, at a larger resolution a black outline would work, but as things get smaller, colors bleed together, so the outline becomes a median of the interior and outline color.
Try not to work on a white background, work on something neutral that won't affect how your eyes perceive the piece. Extremely dark, light, or saturated palettes will not blend will with a majority of colors and can be an eyesore. Grays work with most everything.
Don't be too worried about color count, at this point if you need a color and you don't have it, feel free to add it. When you get more experienced you will be able to make more manageable palettes that can be applied to many situations.
Don't get discouraged! Just work smaller. c: Perhaps an object is a bit too much to take in at this point? You could try to learn how to apply anti-aliasing to simple shapes and go from there! Work on your traditional art skills along side pixel art, pixel art is only one half of the battle, and once you get it down it's a breeze, the part many struggle with is the actual drawing portion. If you can't draw well, you won't have anything to apply good pixel skills towards.
