I was attracted to Autodesk Inventor over comparable programs. I know SketchUp is supposed to be extremely novice-friendly, but I actually found it difficult to do fairly simple things. I ended up giving up. Wasted HDD space. Inventor is very intuitive to me. Being an Autodesk program there's an abundance of support. Heard great things about SolidWorks, too.
I think the best way to start is to have something in mind that you want to model BEFORE you learn the software. Then, jump in. When you need to do something you don't know how to do then look it up. I find the real-world learning (OTJ) to be far more effective for me than trying to essentially study a software before I use it. Boring.
Other than the CAD software you'll need to be able to use slicing software to "slice" your 3D models. I use Repetier Host to operate the printer, and this allows me to generate GCODE from any slicing software I choose.
You'll need filament, probably blue masking tape, a scraper to remove pieces from the build platform, and a shoot load of patience.