Personally if I was to start a Mauser collection I would go with a example of the major models first then delve wherever you want to delve into.
Mine if I was to make one would look like this,
71/84 Mauser (yes it is black powder)
1891 Argentine or 1889 Belgium Mauser (1891 Argentine shouldn't be too hard to find in good condition)
1893 Spanish (specifically due to the squared bolt head)
1896, or 1894, or 1938 Swedish Mausers
1898 Gewehr (used by Germany or other commercial varients such as 1909 Argentines or 1908 Brazilians etc.)
1898 K98k (a nice VZ-24 would also do pretty good here)
With that grouping right there you will have a representation of the major actions and key variations designed by Mauser (and only bought 6 rifles), from there you could easily get into the nitty gritty details on each one (personally with my collections I collect the major models as opposed to having 5 of the same rifle with slight differences but to each there own). Personally I don't really consider my Mauser Vaquero a Mauser as the action is so different (and in my opinion nicer), but if you were looking to add Mauser based actions as well you would have to get a Arisaka of some sort in there as well (and if you go this route the list also continues to grow).