A good way to get started with design and 3D is by creating a 3D packaging design project. It has everything that you need to practice from beginning to end. It can start by working out how the package would work, by creating some small real-life mockups. From there, creating the packaging design in a vector application like Illustrator. You then need to create the graphics for the packaging design, maybe in Photoshop. How will it all look when it is produced? Why not take what you already have and do a 3D visualization. A nice render with great lighting can really drive a presentation home.
Want to dive into such a project? Maybe you just want to see what the process looks like from start to finish. Either way you should check out ColorCubic’s Michael John’s 5 part tutorial on Packaging Design.
Michael goes over everything from illustrator, photoshop, and all the Cinema 4D stuff, including Xpresso for creating a simple rig.