When I started learning 3D software it was much more primitive than what I have now with C4D Studio. By the time I got to C4D I had a good base to start with but even then I needed to get comfortable with the software, this is very important. I first like to make sure I can navigate around the software and get a general feel for it. I would most likely be in demo versions at this point as there is no way id part with cash unless I was 100% sure I will get on with the software, and it will really dose what it says on the tin. I learned this from years before where id jump on a sale for software that I didn't gell with and it didn't deliver quite what it promoted. It took me years before I got C4D as at the time I was considering it, it lacked some essential features like native rigging presets and SSS Sub surface Scattering material for skin. I kept coming back asking questions like has this been added yet, or that been fixed.
Id seek a general overview of the software like on lynder.com, pluralsight.com where they do a "getting started into C4D" tutorial. Greyscalegorilla.com has such a tutorial where you go through a project using various toolsets and its free. I would have had a main objective before I even got the demo, for me it was character design, rigging, animation. Once I purchased the software Id work on getting down to what I wanted it for and use the user manual extensively. I know from experience that the best way to learn is to spend more time doing, than watching videos, so Id think of a simple project and work my way through it. Along the way Id hit brick walls, this made me learn from the manual, tutorials, or forums where others hit the same hurdles. It would by the end of the project tell me some of C4D strengths, and some of it weaknesses and where I need to invest in some plugins eventually.
Once I could get my way around the software and feel comfortable this is where I would target tailored training to my needs, Cinivercity.com has a huge amount of videos. I joined https://cmivfx.com/ and went through some videos on there, but made sure I got through them fast. I would learn a new feature and without delay go off and replicate it over and over again without looking back at the training. Repetition will hold it to memory. By the time I got through a video tutorial, id go off and do the whole thing from scratch without any video guidance unless I got stuck. Once I can do it from beginning to end from memory I know iv got it down.
Now I have always believed that to test myself If I know something well I should be able to explain it verbally, and show it physically, if not then there are gaps in my knowledge. If I cant teach it, I don't know it. This is me personally it may not be a rule for everyone.
If I had to start within C4D without any prior knowledge of 3D then Id do the following.
1: Seek a getting into style tutorial project-based. This will get you familiar with the software in general.
2: Learn to model. this is going to be at the core of most users unless your aim is to use pre-made assets, but you still need to know some modeling regardless.
3: Learn to Uv map correctly, and how to finish off a 3d model asset including texturing, baking, and basic usages of sculpting tools as a modeling aid.
Steps 1 to 3 will cover a heck of a lot of things to learn including modeling principles, what structures to avoid, Hard surface and organic modeling, SDS modeling, edge flow, Uv mapping, body paint for painting textures. There is a good few years to get these things down or at least a year of full-on getting stuck in to get a decent 3d asset made to good standards but thats at a push in this time unless your just geared for it.
4: Surfacing including how to make your own materials including all basics on reflection, refraction, sss, procedural textures.
5: Lighting including basic lighting principles in which photography will teach you allot.
6: Composition, camera set up, and rendering settings.
Steps 4 to 6 will take some time too but your begin to gather some knowledge on these as you go but its good to set their own a dedicated time period to get stuck into these areas. It wont take one pass it it, its a refining process that everyone goes through even after years of doing it.
By the end of it you should be up to modeling an object with good edge flow and polycount, all Uvs done with texture maps complete ready for rigging if needed. This would be a good time if you wish to learn rigging.