Regarding how to organize training, that's a fairly complex topic. Skill level comes into play of course, as does age. Long term athlete development (LTAD) is how we organize our training.
For example:
http://www.judocanada.org/long-term-athlete-development-model/
It is tied into the whole kyu-dan belt rank "model", which I have had issues with "teaching to" for quite some time (couple of decades, LOL?).
I view Judo skill as built on fundamental building blocks/skills/concepts/principles, and of course on basic physical literacy (a word I got from the LTAD model).
So you have general physical literacy (athletic ability, but a less loaded term?), without which \sport specific physical literacy (like Judo) is difficult and painful to build.
Ideally, kids would build up their basic physical literacy (ABC'S-agility, balance, coordination, speed) through a variety of sports/recreational/play activities, and then focus on one or two activities they enjoy. Judo could be one of those activities. Competition would not be a big focus for young kids (or adults starting Judo (or jogging, etc.). Often adults who lack physical literacy are kind of like kids who are starting out in the cycle...
I mean, how many adults who jog or ride a bike for general health do races?
Belt obsession gets in the way of real progress quite often.
Anyway, a bit off topic...