I make these stacking trays inside cigar boxes each shelf has felt on both sides.

You can get sheets of masonite, cut to the same size as your closet shelves, glue felt on both sides, voila you have double your storage space, for about $9 of material and an hours work. and you get to look at them all lain flat on a sheet of felt. i make loop carry handles with ribbon on each side. I like that the air is mostly squeezed out when they are stored.
I also have some Dansco books.

If you have USA subjects they have pages specifically to fit them. you can buy one dime page, one nickle page, one cent page etc. they also have mm sizes if you have alot of one size.
a seven page album costs about $50
In the cigar boxes I organize by country, i focus on certain countries, some types are easy to get full dates sets, some types are one or two year only types.
The books force you to organize by size. for example the 50centimes of the Latin monetary union of southern europe all go together, as do North and central American 10c coins. I have some 50c tunisians, but they are in the tunisia cigar box with the other tunisian silver.
Jamais l'or n'a perdu la plus petite occasion de se montrer stupide. -Balzac