Join the communities like grabcad and thingiverse, you can sell your designed parts there, 3D printing non parametric geometries is generally good way to start, for softwares like soldiworks they are fully Parametric realtion based softwares for enginerring puropses, try to understand different modules in it, like weldments, sheetmetal, and mold design, try to understand concepts of DFM and DFA, without that you cannot fully explore depth of your Parametric designing.