I recommend picking up some better software for drawing in than MSPaint. I haven't used it myself, but Paint.net is meant to be very good, and it's free. If you can get a copy of Photoshop, you can't go too wrong with it.
Other than that, just keep on practicing.
I've not used them much yet, but I grabbed some of these recently. They're a really brilliant white which highlights very well on toned paper.
IMHO, this drawing looks good but lacks contrast. But really, reddit community may not be the best place for you to feedback on your pictures. There are several online photo feedback platforms where you can get feedback on your pics from hundreds and thousands of people.My favourite among the lot is Famingo and 500px, because perception of pics depends on a lot of factors like age group, sex and region(in other words, culture) of the people voting. You should set your audience as per your requirements and try out multiple tests. Apart from just statistically showing you how a photo looks, you'll also find out how it fares against other pics in your region, age group and gender, which can very helpful when trying to set yourself apart from the mob out there.
I was also thinking the same thing of buying this: Speedball PH Coate Artist Willow Charcoal Assorted Lengths 30 Sticks, Black https://www.amazon.com/dp/B001PNG4LA/ref=cm_sw_r_cp_api_i_dlC_InjNFb9BT3ZCW
Try Petter Hegre. He basically specializes in nude female photography if that’s what you’re after.
If you really want to get better at drawing the human form though, tracing photos isn’t going to build your skills all that much. You’ll pick up a few things, but the progress will level off pretty quickly. I strongly recommend Figure Drawing: Design and Invention by Michael Hampton. He does an excellent job of explaining gesture drawing and how to make the transition from gesture to volume. Andrew Loomis is also great. For videos check out Stan Proko on YouTube.
Looking through all these books I felt like I had to mention two very highly regarded figure drawing books as well:
You're off to a great start! If you have the patience to do studies like this then you'll go far. :)
Loomis is a really great resource, and there's a tonne you can learn from him, but he won't make you a great artist on his own. It's very important that you also draw from life, especially when you're a beginner. This is to develop your 'artists eye', an intrinsic sense of proportion that can't be taught but only learned through practice. You don't have to draw figures, but drawing anything from observation will help to develop this sense, which will in turn make you better at drawing figures. As your skills develop you will do less literal copying and more interpretation, but that will take time.
Two resources I would recommend for this are first 'Drawing on the Right Side of the Brain' (you don't have to read the text, a lot of it is pseudoscience, just do the exercises) and then later the Charles Bargue Drawing Course (you don't have to do the entire thing, but certainly try more than one).
In addition to this, I'd suggest attempting some more gestural drawings. Gesture is a hard concept, but proko does a decent job of explaining it. Basically, don't worry too much about drawing fully outlined bones or perfect proportions just yet, first capture the force and weight of the pose. Do this in combination with drawing from observation and you'll be surprised how much more believable your figures will become.
Good luck!