My World coin collection is, to say the least, very diversified... no specific 'Type', 'Country', or subject matter. I usually focus on esthetics, the collaborative results of both the designer and die maker, then, of course, it's condition, and, sometimes, just the History attached to the coin caught my eye. I never tried to become an 'expert' in any specific coin category.
I wound up with a coin collection most collectors wouldn't want... lol