I'm posting a very limited answer because the real scope of it.
I want to learn Graphic Design from scratch and be job ready in this field.
I must say I have lived all my life doing "graphic design" "related" things, for example in high school one periodic table that was stoled two days after by a fan. I studied 4 years in the university, and worked on the field by several decades now. And I still "strugling" to be ready, because things are changing all the time.
Having said that, part two:
Art and design are not the same, take a look at this: Whose persona should I consider while designing my portfolio?
And the marked as duplicated answer: What does an artist who wants to learn graphic design need to know? among other things.
Part 3, the software... Oh, my.
The software is specific about what branch of graphic design you want to work in, and the first choice is what do you want to do?
The main categories based on the output
Based on the specific step of the process (this list is not methodological but a brainstorming.
Image manipulation, photo manipulation
Ilustration creation
Press output, publication integration
Web UX, content
Motion graphics
Corporative design, internal comunication
So the main categories in which "Graphic design" software is categorized is:
Vector based: Corel Draw, Ilustrator, Inkscape, and some others like DrawPlus.
Photo editing: Photoshop, Gimp (and some many others)
Publishing systems: InDesign, QuarkXpress, Scribus
Presentation software
Video Editing
Animation
3D, animation and rendering, modeling, etc.
So first of all you need to decide what are you going to do.