When I first got into collecting the slabbed Morgans, my goal was to complete the entire set in MS. I soon realized that I didn't like the looks of a lot of them in grades MS60-63. So, whenever I could afford it, I would buy them in MS64-67. I also realized that I would never be able to build a complete set in MS, and I didn't want a set that had "Good this", "Fine that" and "XF whatever" mixed in with a bunch of AU to go along with the MS I could afford. To me, it would have looked more like a menagerie than a well-balanced collection. So, I resigned myself to buying whatever I could afford in the highest grade possible. It doesn't matter if I have a dozen 81-S or a boatload of 82-CC with assorted VAM's, DMPL's, GSA's & toners to go with them. I'm having just as much fun, anyway.
If I were just starting a Morgan collection, I would go through a price guide and list those I think I could afford in MS66 (or higher), which ones I could afford in MS65, and then shoot for MS64 in the rest (well, except for a few still too much for me even in MS64). Unfortunatley, I didn't think of this until after I had already picked up quite a few MS64's. At some point I'm going to have to start upgrading. Would be better to get what you want to begin with.
The Red Book guide Morgan Silver dollars lists optimal collecting grades. For example, the one Carson City I have is a 1884-CC, and the book suggests MS-65 (which I have).