It's important to practice using references. Otherwise you will be teaching yourself bad habits and inaccurate anatomy. It will be much more difficult to relearn how to draw things correctly. That being said, it's also important to take what you have learned from your practice and put it to use. It's good to try to draw things from imagination, then you can figure out how well you're grasping what you've been practicing.
the last pic is nice but the anatomy is off. shes quite short so im assuming shes a young teen which means she developed early because her boobs seem to big for her age group. The hair is sticking out the side/top of her head weirdly and the way she holds that sword and what im assuming is an overlap of her hair on the sword shes going to cut half of her hair off. Hair gets in the way when you move around (i have long hair so trust me)and with a sword that is bent like that it would be even more at risk of getting in the way. i wouldnt complain if she did have a ponytail or braid on the opposite side of her head to keep it away from the sword. the bow feels like it was put there to cover up how her hair is tied into the ponytail (google image ponytails and you will see its quite simple actually). I cant tell if thats just a couple random lines or if that is a knot on her lower left hip opposite the slit. if it is a knot what is it holding together? its way to thin to hole her skirt up and on the wrong side im fairly sure. if not then never mind.
and its allways good to use ref. No matter what you are doing (unless its just from your head and nothing you are drawing is a real thing that you can look up ref for. but even then it helps) its just helpful and brings a believability factor to it all. this picture http://www.gamingangels.com/wp-conte...ck2vasquez.jpg was done by Jhonen Vasquez who is a professional artist and he himself said that he needed reffrence for it. So this shows that you dont have to copy exactly what is there but you can use it to place things in a more realistic manner with reffrence.
Even with the perspective, the hand is too big compared to the body. Also you should do something about the yes, like color them or something!