Nice pics! I think the third one is my favorite. ^_^
As for arms and legs... It's hard to give advice without seeing any of your figure drawings, but I'll give it a shot since I'm taking a Life Drawing class. I'll just repeat some things my teacher said.
It's best if you can get someone to model for you, so you have someone still to look at... but even if you don't, you can still observe some things about the human figure. (... or you could always employ a mirror.) Look at parts in relationship to one another. For example, see where the elbows are in relation to the rib cage-- the elbows are just about where the rib cage stops. The hands, if hanging at one's sides, are about at crotch level. Observe how long the legs are in relation to the torso. etc. Then look at how the joints connect. For example, a lot of beginning artists draw the thigh joints straight across... but really there's a "V" shape. And the neck doesn't start level with the shoulders, but farther down in the front. Those are some things to look for. Also muscle structure, etc.... If you're serious about it, get yourself a good anatomy book. (Even if you're only doing anime, it will help.) Hands and feet are the hardest to draw, so don't feel discouraged if they look strange at first.
I hope this helped! Good luck, and please show us some more of your drawings!
upload some of your full figurer drawings and im sure we can give you some tips