You can actually learn most of the important aspects of 3D and computer graphics using only free software. Most of the industry however uses a lot of very expensive commercial software.
If learning in a school environment, we recommend using primarily whatever software is used in your classes. It's always a good idea to learn additional packages as well, but focusing on the software used in your classes will help you get the most from school.
If learning in a self directed fashion, we recommend starting with free software for your core needs and then expanding with any additional commercial software that you are keen to learn.
Blender's built in renderers (either the default or the new Cycles renderer)
Image Editing
Gnu Image Manipulation Program (Gimp)
Krita
Video Editing and Encoding
Kdenlive
FFMpeg
Blender (Yes, it has a video editor built in!)
Recommended Commercial Software Note: If using the free software above, you don't necessarily *need* any commercial packages, however, many of these packages offer additional functionality, and can be quite useful.
Photoshop
Maya
3dsmax
Composite (now included with both Maya and 3dsmax)