A Beginner's Journey

[Vipershark]

Hello!
First and foremost, you'll want to check out our Spriting Dictionary.

Aside from that, you have a few issues that need addressing.

First, instead of using a white (or in your case, transparent) background, it's best to work on a background color that's desaturated and stands out well from the colors in your sprite. It's good to pick a hue that appears nowhere else in your sprite, if possible. For one, it makes it a lot easier on you when working with your sprites, and it also helps others to clearly see what is or is not part of your sprites.

In addition, your sprite is using pure black (0,0,0) which you should avoid if possible (along with pure white, (255,255,255)). (Particularly because Paint and some other programs don't play well with transparency and turn it pure black, which totally screws up your sheet when people open it up.)

As far as the sprites themselves go the biggest issue you have is that your colors are flat.
You need more contrast between your shades to make them stand out better. How do you achieve that?

These are some of the colors that you're using.
Notice how their Hues (238, 84, and 156, respectively) are pretty constant for all of the shades.
Color is three-dimensional, and your colors are only really changing in one dimension, Luminosity/Brightness. You're adjusting how bright the colors are and you have some small changes in saturation, but leaving the hue completely unchanged. Because of this, your colors appear flat as they're quite literally one (or two, sort of) dimensional.

To fix this, you'll have to use Hue Shifting as well as change the saturation between your shades so that they become fully three-dimensional.
When hue shifting, you generally want to keep in mind that brighter shades hue shift to warmer colors (so your brighter greens will tend to be more yellow) while your darker shades hue shift to cooler colors (so your darker greens will tend to be more blue). For saturation, you generally want your base colors to be more saturated while your highlights and darker shades will be less saturated.
This doesn't cover every possible situation of course, but that will generally get you on the right track for picking a better palette.

I made a quick edit to change your background color and gave the pure black a slight bluish tint so it's no longer problematic.

See if you can fix your colors from here.
Good luck!

There are also a lot of anatomy issues, but unfortunately I'm not really the best person to tell you how to improve that.

BTW, what are the bumping rules for this place? Am I allowed to post again after I've already posted if I have a new/updated sprite?

If nobody else has posted and it's been at least a day, bumps are generally okay in your own thread. Otherwise just edit your most recent post.