I dont' think a specific software or material (such as brush or paint) create good art, it's mainly the artist (your mind!). I have professional concept art friends that after years using digital art (photoshop, z-brush, maya), they went back to traditional. And they think that their traditional art is somehow better than the digital stuff they do. Photoshop is just a tool that allow them to mass produce concept art for a very demanding game/cinema industry (i.e. easy to modify the layers, easy to erase and redo something).
If there is a very special reason for you to just use photoshop, then go ahead and master the software, it is always good to learn something new. But mastering photoshop is not the same as mastering the basic principles of colour/lighting/composition/storytelling. That's why I asked about the sketches. Even when I do my traditional paintings, I do a lot of planning: think about the story, sketch the characters, plan what they are supposed to be doing, sketch the scene, test some colours, and then I move on the the big piece of watercolour paper.
If you are lacking internet to find references, just go outside and take some photos with a handphone (I hope you have one!). If you need references of human-style poses, hands, faces, just take selfies (or ask someone to photograph you in the pose you want), this is sometimes better than finding references only because you can be more specific about your own poses and photos.