The CRAFT of 3D printing is NOT in the printing.

Running the print machine is a skill. CNC (Computer Neumeric Control) takes the creativity out of machine operation. Pressing RUN is not much of a skill.

Machine operation IS a very technical skill, with lots of variables that need to be observed and corrections made (usiually in the g-code) to obtain a satisfactory print. Usually stopping the printing operation and starting over with corrective g-code. These corrective edits are a skill that improves with time and experience. .

The true creative effort is displayed in the design and use of CAD (Computer Assisted Design) skills.

Beginners do need to print "other peoples Junque." It's fun to see the machine operate. 

However, to become a true craft, I consider original design to be the actual and only CRAFT in 3D (hobbyist) printing. 

Simple 3D CAD software exists and some of them are free. Search "Free CAD" for examples.  No need to list here. I don't have a recomendation on free software.. 

Personally, I have several purchased versions of 3D CAD sofware. All were obtained well before my interest in 3D Printing. Autodesk, Vectric, Rhinoceros, DeskProto, and several others are installed in my computers. Fusion360 (Autodesk) is usually my go-to 3D print CAD,

My "Quick Thought" is, "Start designing and printing ORIGINAL work." Then explore CRAFTing ideas with colors, assemblies, blends, and the thousands of variables possible with 3D printing. But... that's just my opinion. DO (or print) whatever is fun for YOU!  ~Dan