I find the easiest thing to do is lay out the timeline as an Illustrator document that is comp height (1080 typical) and wide enough to include the entire timeline. You add all of the elements that you need in your timeline where they should go and put everything you need to animate on its own layer. Then you import as a comp and nest that comp in a standard sized main comp. All you need to move down the timeline are a few position keyframes. You can add additional elements to the main comp or just jump into the nested comp to animate the various elements as they come by.
Parenting is also a really good option. If I add something like a video or an animated graphic to the animated timeline it would just go into the main comp, the in and out points would be set and then you make the nested comp the parent and it will keep it moving right in sync. The initial design and layout of a timeline is the most difficult part. Deciding where you should cut to a different angle or transition to a new element should be based on the narration that goes with the timeline. Each of those cuts or transitions should be a separate comp.
Almost all of the timelines animations that I have ever worked on had a minute or more of copy to cover but most of my comps did not cover more than a sentence or two and were around 10 seconds or less. It's a lot easier to break things up into manageable pieces than to work on a five or ten-minute comp with a couple hundred elements arrange.
If you are very new to AE I suggest that you spend a couple of days learning Basic AE. You need to be very familiar with layers, nesting comps, pre-comps, preparing artwork for video and the basic principals of animation to avoid frustration and do a good job.
AdChoices