I very quickly realized the owners manual supplied by the manufacturer is generic at best and leaves a lot to be desired. There are dozens if not hundreds of parts on your coach that are not included in the basic book. I began collecting information on all aspects of my motorhome and continue to this day to add information. The internet is very useful for this task. I file every new addition into a binder and keep it in the coach. This has helped me numerous times over the years when something didn't work. I keep manufacturer contact information as well as document when something breaks and needs replaced. I frequently look at why the particular part failed and think about ways it could be improved to work better or last longer. This is an on-going project and yields a degree of comfort as you progressively make your RV better.
There is no real priority list that applies to every RV but rather a need makes itself known and you take care of it in such a way that it doesn't keep happening.
I always keep a notebook in the coach and make a list of items to take care of, either right away, or when I return home from a trip. On our current trip that began in October, I have over 50 items in the list. Some are already taken care of and some I will do when we eventually return home.
RVs are notoriously unreliable due to financial considerations when they are built. This is my way of making my coach more reliable and thus more enjoyable to use.
Good luck with yours.