No idea where to begin!

My budget, well I would like to keep costs down but I know I'm gonna have to spend some money. I'm doing my self because I want to learn how to do it, sure I can pay someone but then I won't know how to do it hahah and no I haven't done it before. Yea I will post some pics.

So start at the rust spots, what about minor dents? I bought a hammer and dolly set.

So I figure first is sand down the area with a sanding block? What paper grade?