i think defining the purpose of your piece should always be the first step, it is the most important step in making a piece of art. it's kind of like thinking before you act. you want to have a goal and purpose in mind. it doesn't have to be great and meaningful. something as simple as studying or practice is fine. i think this is important, because without it, without a goal, you would not be able to personally determine if you had succeeded or not.
drawing poses is an important ability to have. characters are quite often the subject of interest in paintings.
how i begin is doing what i think you've done, you say you drew stick figures. the term artists use is gestures or thumbnails. they look like this:
to do good thumbs, you'll need to have an understanding of the human anatomy and the transfer of movement and weight of fat and muscle on the skeleton. you'll also need a good grasp of the rules of perspective. you'll want to keep these simplified, carefree, and fluid. with your goal in mind (to create a comfortable, relaxed leaning figure holding a gun over his shoulder and a smoke in his other hand, looking badass, confident)
you should make a few, pick ones you like and embellish them by making other variants of it, try showing it from different perspectives. once you have the one you like, enlarge it some so you can fit in some loose detail to get an idea of what the end result will be. again, it's thinking before you act. You're basically trying to decide, "is this worth drawing? or not?" and try to make visual notes of what needs to be done to get there.
assume that step is done. something you'd like is a background, to contrast the modernness of the character, to make him feel out of his element, making him more interesting. there are many more ways of achieving these goals, other than the obvious. you could try making anything old, use darker colors, and newer things use lighter colors. it gives the painting conceptual depth. i think the best paintings have these. god is in the details.
the setting you've created isn't describing what you've written, i'd say you're failing in that area. what you hoped it be saying, isn't being spoken. the bricks, cement, asphalt, plaster walls, all look very quick and bland. not very descriptive. you need to work more on your rendering, and use painting techniques that visually describe the material as what it is. use reference.
your bricks look pretty messy. you need to work on what's called your craftsmanship, basically it's your ability to keep it within the lines, making those lines you're keeping within, straight, smooth, and sharp. clean gradients, solid deliberate blocking. basically, you need to learn how to write like a girl and apply that steady hand to your artwork.
also, you need to work on your understanding of color theory so that everything in your scene is harmonized with one another. you also need to work on your ability to render forms.
i've found that composition is more than just the balanced arrangement of forms and how they interact with one another. composition can be much more than that. it can convey moods and control the eye. every
element is rooted to the composition. the slight shift in hue of an edge, can change the entire effect of a piece. every line, every space matters. a large part of your composition is controlled by the lighting of the scene, and it should be thought out ahead of time.
i think you should give it another go, and i'll get you some feedback at each stage.
i hope this feedback is helpful. it's the least i could do after you filling out a form and not really get much from it. my intention with the form was to point out how disjointed everything felt, your themes were not harmonizing.
if you're willing, lets start at the beginning, and try to make this piece better, to hit each stage of the painting process so that you'll better understand it.
make some thumbnails with the same goals as before, but lets try a viewpoint that will amplify the feeling you're looking for; views that make him look more badass. my first reaction is to try a lower view, looking up at the figure.