Best advice I can give you about time skips is to think of the story more in terms of scenes and events than in terms of linear time. Most modern long-form stories are told in sequences of scenes that focus on key events, and the connected events tell the larger story. I find it's helpful to think of scenes almost as self-contained stories in and of themselves: characters are introduced, there's some of significant action that takes place or some kind of problem that presents itself, and at the scene's end the situation either resolves itself, or is left intentionally open with an implication that it will be resolved later.
Thus, telling a large story is a matter of breaking it apart into its most significant events and arranging them. Here are some general rules to keep in mind:1. The order in which scenes are presented should make sense
. This doesn't mean the story has to follow a perfect linear chronology, it just means that the reader should be able to follow what's going on. For instance, if you have a scene where a character is eating breakfast, followed by a scene where a character is at work, the reader will probably have no trouble following the story: the guy had breakfast in the morning, then afterward he went to work. Here, the reader will just assume time is passing normally and linearly, without really needing to know exactly what time these events are taking place.
Conversely, if you have one scene where the main character is eating breakfast, and then in the next scene he is suddenly on the moon, this is an abrupt transition. What the reader will probably assume here is that you are intentionally jumping forward quite a ways in time to draw their curiosity. The assumption is that the next few scenes are going to involve traveling back
in time to show the sequence of events that led to the character ending up on the moon. If you don't do this, the reader will be confused: if the character is eating breakfast in one scene, then suddenly he's on the moon, and then the rest of the story is just about him doing stuff on the moon, the transition will feel jarring and unsatisfying.2. Every scene needs to matter.
Any story is going to be filled with any number of events that happen on and off camera, but not every event is going to be turned into the focus of a scene. Which events become scenes is entirely up to you, but any scene that gets included needs to have some justification for being in the story. It needs to either advance the main plot (or a subplot), add to the development of one or more characters, or provide some kind of basic entertainment value (sex scenes and random funny scenes would fall in this category; you'll want to use these kinds of scenes sparingly).
For instance, in the example I gave about the guy who eats breakfast and then goes to work, there is a large sequence of events that is probably taking place: he's asleep in bed, then he wakes up, then he puts his pants on, then he eats breakfast, then he probably shaves and showers and whatever, then he gets in his car and drives, then he sits in traffic for 45 minutes, then he parks, then he goes to the office, then he's at work. However, this entire sequence of events is covered in two scenes: the guy eats breakfast, then the guy is at work. The reader infers the rest.
Both of these scenes serve a purpose in the larger story: the breakfast scene establishes some basic things about the character and shows an episode in his normal, domestic life. The work scene establishes what he does for a living, and if his job or his workplace is essential to the main story, this is also an important scene that moves the plot along. Thus, even though there are any number of additional events we could cover, do any of them need to be scenes? Probably not. Sure, we could have a scene where he's brushing his teeth and a scene where he's sitting in traffic, but would either of those scenes add anything meaningful?
Conversely, we could swap out the scene where he eats breakfast for a scene where he's brushing his teeth, and it would convey the same essential information without affecting the continuity. In this case, we need to think about the story overall: would a teeth brushing scene be a better illustration of this guy's domestic life than a breakfast scene? If it matters, use the one that works best; if it doesn't, it's dealer's choice. Get used to thinking like this.3. Scenes should begin and end appropriately.
Every scene needs to begin somewhere logical, and there needs to be at least some level of basic continuity between the end of one scene and the beginning of the next. For example if a guy is eating breakfast at the end of scene one and is at work at the beginning of scene two, there is a logical continuity. If he's eating breakfast and then is suddenly on the moon, there is not.
The same applies to how you end the scene. Whatever is at stake in the scene needs to be resolved; it makes no difference whether your characters are fighting a giant robot or making sandwiches for a picnic. If you end the scene on a cliffhanger, the cliffhanger must resolve at some future point in the story. If a guy is fighting a battle and then suddenly the scene just ends, and we never find out who won, it's unsatisfying. If we never even knew why they were fighting in the first place, it's doubly unsatisfying.
So, looked at from this perspective, the issue of time skips becomes far less important. Time can fluctuate in a story: the events of an hour can take up multiple chapters, but in a later chapter you could gloss over an entire week if nothing important happens. There are stories in which periods of years or decades are skipped over between scenes. Time is much less important than constructing your scenes well, focusing on essential events, and omitting mundane or uninteresting ones. Hope I was helpful.