The best way to get better at drawing from your imagination is to practice drawing things in real life.
I know that doesn't make much sense, since there's no such things as dragons in real life, however, all mythical creatures are actually based on realistic animal proportions. Even if a creature is mythical it still follows the basic animal skeletal structure; skull, spine, ribs, tail, digitigrade legs, toes, ect.
So if you practice drawing four legged creatures and studying the anatomy and skeletal/muscle structure of real animals, then drawing and creating your own animals will be a piece of cake.
Most dragons have the skeletal/muscular structure of a dog, but of course things are changed according to the artists preference, and sometimes artists mix the skeletal structures of different animals to make a dragon, but overall most dragons are comparable to a dog. And dragon wings are usually based off bat wings, so I would suggest looking up some pictures of those as references.
And of course for skin references you could try looking up reptile skin patterns, although fish have nice scale patterns as well.
For drawing anthro's you need to learn how to draw both human and animal anatomy, since anthro's are a mixture of animal and human. Once you learn how to draw humans and animals separately it will be easier for you to mix them together in the way that you like, so your drawings will be able to better communicate what you want people to see.
Here is a great in-depth tutorial about drawing anthro's.Following tutorials help, but you can't get any better practice than drawing from real life, since you can better see the dimensions of what you're drawing and can get a better understanding of the shapes involved in the body and how the light affects their appearance from different angles.
As for the second sketch you made, it looks nice, but you need to work on a few areas like the breasts, legs and shoulders.
Her shoulders are a bit too rounded off, so they need to be a bit more angular, and her neck is a bit too thick.
Here's a picture to better explain what I'm talking about:
As you can see, if the neck is upright, it's straight, then slopes into the shoulder, which lines up with the collar bone, so shoulders aren't really all that flat. And as mentioned earlier, shoulders come up a bit more than what you drew them, and they should lead into the collar bone, rather than merging into the neck.
As for the breasts, they're a bit too round, whereas breasts are actually a shaped a little like an oval, they're also a little too high.
Here is a simplified tutorial on breasts, but again, nothing makes better practice than drawing from life or real picture references.
You should not be able to see the tail like that from the angle she's standing at. The base of the tail is an extension of the spine, so it should be behind her, while the end of the tail may be poking out from the side. Also her waist is a little too short.
The legs are also a little too short, but I can't blame you since digitigrade legs are hard to draw, but the anthro tutorial I linked earlier should help. However, her left leg is at a bit of an odd angle. She is facing us forward, but her ankle is at an angle as if she was facing sideways, while her toes go back to facing forward, whereas the ankle should be more aligned with the leg/foot so that it better fits the angle she's standing at.
Aha, sorry I made that so long, but at my job I'm an art mentor, so I'm used to giving lengthy critiques.
I'm sorry if I was a bit too harsh, but I am in
no way trying to tear you down or be mean, I just like seeing artists improve and succeed, and critiques help them do that.
You have potential, you just need a bit more practice.
Hope that helps.
