To answer your question, if you're interested in digital drawing, I'm of the belief that you should jump into it as soon as you can. The 50% rule from Lesson 0 is a great opportunity to play around and experiment with it. Just like with everything else, don't get yourself caught up in the whole "I'm not ready yet" mentality.

Now, looking at the first section of the challenge, I noticed that you appeared not to notice the point I raised in bold in the homework assignment section - specifically telling you to vary the rate of foreshortening across your cylinders. In general, with any and all of these challenges that have you drawing many of the same thing you should be varying whatever you can. Rate of foreshortening, orientation, etc. Laying everything out straight down and effectively repeating the exact same thing over and over ad nauseam is not going to do you nearly as much good as exploring the full scope of the challenge within the bounds of the exercise.

While you've done a decent job with the alignment of your ellipses, and you certainly checked them thoroughly and conscientiously, you definitely got tunnel vision when it comes to everything else. For example, you appear to have neglected the core principle of perspective - as something moves away from the viewer, it gets smaller. You quite regularly drew the far end of the cylinder either equal in overall scale to the end closer to the viewer, or slightly bigger.

Foreshortening can be seen in two ways. There's the basic one described above - things get smaller in scale as they move away from the viewer. That one's the easiest to understand. But it also has a more subtle impact to the proportional width of that far end, which is what we treat in cylinders as the shift in "degree" from one ellipse to the other. You were aware of this, and did apply it - but what you missed is that both this shift in degree and the shift in scale go hand in hand.

The amount by which the far end is both smaller and wider than the closer end tells the viewer how much farther away it is. From this, we can understand whether the cylinder itself is long, or short. But if, as with all the cylinders you've drawn here, the farther ellipse is the same overall scale as the closer one, that tells us that there's no distance between them, and the cylinder has a length of 0. The width, however, since it gets wider as we look farther back, tells us that there is a concrete length of this cylinder. What results is a contradiction.

We cannot logically end up in a situation where there is a dramatic shift in degree, but a minimal shift in scale, or vice versa. And we definitely cannot end up in a situation where the cylinder has a length of 0.

Now, despite the fact that there is another 100 cylinders in boxes here, you've effectively attempted to do the same thing with them, drawing effectively the same thing over and over, without consideration for variety. This is entirely against the spirit of this challenge, and the course as a whole.

As such, I'm going to ask you to complete this challenge again, and submit it separately for a new, full critique. You may want to take a look at what other students have submitted for this challenge to get a better sense of how it should be approached.