It really depends, I think. Personally, if the drawing is small enough to fit into the scanner, and if the scanner is pretty good at not utterly killing the colors or shading or whatever of your drawing in the process, I would go with that option.
Otherwise, if it's too big, or if it's framed or something, then I guess you could try taking a photo of it--preferably with a good camera (perhaps in HD?), and preferably framed within the camera so that the drawing is properly presented in the photo to the best of your abilities.
Presentation is everything; you could have an amazing drawing, but if it isn't presented right, it'll take away from the drawing. Way too many times do I see muddy, dark, or crooked-looking photos whenever people go that route to show their drawings--heck, I certainly wasn't perfect with a camera myself, as shown
here with the 'frame' around my drawing ending up crooked, but I did my best.
I don't have to deal with these extra issues of properly presenting the drawing and all that if I just scan the drawing in, although there will be some times when you'll need to digitally edit a picture--perhaps to crop out some empty space to place more focus on the drawing itself, or to fix some scanning errors that might occur (like the aforementioned "killing the coloring or shading" bit). It certainly looks weird, for example, if you post a picture of a drawing that takes up only a corner of the page, and you leave in all of that extra white space.
I don't know much about Photoshop, only having dabbled in it a few times while on a school computer, but as for tablets, I tend to hear people say good things about Wacom tablets (they're basically a standard). Cintiqs in specific are the ones people are looking into nowadays, since they have screens that you draw directly on, as opposed to having the little tablet beside your computer and drawing in this awkward position where you're staring at your computer screen instead of down on the tablet, like you probably would if you were drawing on paper and all. Cintiqs are pretty expensive, though. A regular Wacom tablet (as in, the ones without the draw-on screen) should be just fine and be more within your budget.
Um...I don't really have much advice with regards to how to go about improving your skills, except for the usual; use references, use your
own body as a reference (practicing poses in a mirror or staring/studying your hand, to figure out what looks right and natural, I guess?), and, as always, just keep churning out drawings. The more you draw, the more you'll improve, even if it's just a bit at a time.
So...hope that helps? ^^;
