As far as the order of what you should focus on, Index about nailed it.
Air sealing should be first. Stopping warm air from moving out or in is number one. In an older house, you don't have to worry about it being too tight, you'll never get it all, but you can slow it down. Over the course of several years I have hit parts of my 1920 house basement, walls, windows, and attic with caulking and spray foam. Honestly, I have EASILY covered 4 ft x 4 ft area.
Two months ago the energy audit guys (Mass Save) here in, well, Massachusetts, did a blower door test, professional air sealing, then another blower door test. Try and get that.
Next hit your attic, probably R-40 ish would be fine. IF it is properly air sealed, doesn't much matter what you use as long as a vapor barrier is used where appropriate. If not air sealed, don't use fiberglass - only insulates, but does not stop air flow.