O.k. Let me dig into this one a wee bit.
Here's how I have been taught the method. Although we lay out the cards in a sort of
maze method, we don't necessarily have to follow the maze card-by-card when reading the cards. All of the rules of the Method are more fluid, even though I know Camoin presents them in a L'Empereur-like manner.
So, in your example, I
might take solely Le Monde to be the solution to XIII-R, but if it were salient to the reading that
both Le Diable
and Le Monde were a combo-platter, then both cards together-- perhaps even left to right-- would be the overall solution. The strength of this method is its use of relationships between cards, whether that relationship be a type of gaze, repetition of a symbol, variation of a symbol, repetition of an idea, variation of an idea, etc.
So, I know I have seen some students on Camoin's site get into this 1...2...3...4...5 method of leapfrogging around through the spread and following gazes, and reading cards in a particular order. To be sure, this may serve the reading well. My teachers have simply not been as rigid, and these folks really hung out with Camoin and learned it very well.
My teachers of the method of course have used the gazes when laying out the cards, but only use the gazes when reading the meaning when it seems salient, given the context of the question. For example, when L'Imperatrice and L'Empereur gaze at each other (or not) this is salient for a reading about two people connecting on a project. I have not seen as much emphasis on following the gazes directionally when reading the cards. But, ya' know, I never could ask Camoin, himself, about this. So, I could be wrong.
So, back to your example, La Justice moves upward to Le Diable in the Present column. Well, this could be read at any time in the reading and need not be read in any particular order. As I mentioned, Le Diable could be related symbolically or ideologically to Le Monde and is thus connected to Le Monde, as Le Monde sits above as the solution for XIII-R. So, it could be read this way. Maybe it is significant that Le Monde gazes at Le Diable in the sense of the meaning of the reading; maybe it's just the gaze methodology and the meaning runs from left to right (Le Diable to Le Monde). The context of the question helps.
FOr example, if your spread were about a mother (VIII/XV) who was anxious about allowing her children (XV) to take a trip (0) to Europe(XXI), Le Diable --> Le Monde shows binding of a protective mother with freedom. This has a transformative effect on them (XIII) and greatly expands their horizonas (0 --> XX).
In any event, once XIII is uprighted, we see XX.
Just a final word on "don't look at a card until the uprighted card's gaze points you there". Yes, this is a guideline, but fluid. In actuality, it may be salient that the cards are NOT looking at each other, yet, until the solution is applied. So, this point may be salient for the reader or querent. This is why, after awhile, I think many people like to get all the cards out as a sneak preview (or movie trailer) of the story.
Does this help or obscure, Flavio?
(PS) We should inquire on Camoin's site and get different views about whether Camoin says we follow gazes even right-to-left when reading the cards and not just when laying out the cards. I've been taught the method with more emphasis on laying out the cards, but being more left-to-right when reading them, unless the gaze-following is especially salient. Whew! Perhaps that's all I needed to say.