I am also mid/late fifties, so understand the frustrations of trying to find things that don't age us further! I personally adore my Bare Escentuals eyeshadows, but they do have shimmer (I find that a bit of shimmer actually looks BETTER than matte, but that's just me), so I would recommend Bobbi Brown's eye palettes. They have mostly matte shades, although one or two in the palette might have a tad of shimmer.
There really isn't a lot that can be done about sagging skin, IMO, once it appears, short of plastic surgery, which I am not about to undergo, but I do really like the Bare Escentuals Rare Minerals Eye Cream - it's one thing that I have been remembering to apply every day. It seems to have softened the crowsfeet at the outer corners of the eye, and it's supposed to help with crepiness as well, but I don't often remember to apply it to my lids.
It's important to do a bit of exfoliation several times a week - this really helps my skin look its best. My BE RM Cleanser has an exfoliating element to it, but it is also somewhat drying, so I don't use that cleanser more than several times a week. Otherwise, I like to use my Mary Kay cleansers, either the Timewise or the original creamy cleanser for dry skin. Mary Kay moisturizer, or BE RM Moisturizer, is basically all I use. I try to remember to carry it down my neck as well, but often forget.
I think that a lot of how you age depends on your genes, and how much you've exposed yourself to the sun through the years, and so I don't go crazy buying ridiculously expensive creams, etc. The die has already been cast by this age as to how I am going to look. LOL
But I LOVE playing with color, and have purchased nearly every brand of cosmetic out there at one time or another. My personal favorite line is Bare Escentuals. LOVE the blushes and eyeshadows, and just have so much fun picking out colors to wear each day, even though I tend to stick with neutral browns, bronzes, and taupes. haha
I don't wear an allover foundation, though, because I think that it ages me. I just spot conceal a bit with my BE Well Rested (because I'm a warm skintone - a cool might use Bisque or Summer Bisque or whichever Bisque is right for your coloring) and apply some undereye concealer.
Undereye concealer makes a HUGE difference in my appearance. It just brightens up my face. Favorites include Laura Geller's Caulk Pencil, Mally's Cancellation Concealer, and Philosophy's Airbrush Concealer.
I also look better with my brows 'done', and the first thing I apply each day is my Smashbox Brow Tech in Taupe. Just the powder, I don't use the wax part. Brows frame your face and really add to the polished look.
For blush, I love to use a BE Radiance or blush, but also like Mally's or Laura Geller's Blush n Brighten. It would depend on your particular coloring as to which shade is most flattering for you. I am a huge believer in knowing if you are warm or cool and going from there. I am a warm and look MUCH better in warm makeup tones. Cool tones make me look awful. Bobbi Brown's Rouge Pots are nice if you can find a flattering color in them. They are very different from my BE, but give a nice, dewey look.
I have fun with eyemakeup, and own way too many eyeshadow pots and palettes, but makeup is one of my few vices, and everyone has at least one or two, right? LOL I will usually only use two colors on my eyes - one for lash to crease, and one as browbone highlight - and usually it is a brown/bronze, which is most flattering for my green eyes.
Mascara loves are BE's Buxom Lash mascara or Mally's Volumizing mascara. And in the past year or so, I've had fun doing 'tightlining' on my upper lid. Don't like the look of it on the lower lid, but the upper lid - dynamite. :) SB's Jet Set or BE's Insider Liner are nice for that.
Lipstick is another favorite cosmetic, and I never leave the house without lipstick - I need it on my somewhat small mouth. I also use lipliner to help keep the lipstick where it's supposed to be, and also like BE's Lip Primer for that purpose. :) Dark, brownish shades are just not flattering at this stage of life (were they ever? LOL), and my whole face brightens up when I apply my lip color. If you don't have too much problem with feathering and love a minty blast, I highly recommend BE's Buxom glosses, or their 100% Natural glosses, but the 100% Natural ones feather MUCH worse on me than the Buxoms. Beautiful colors, though. Today I am wearing Cupcake in the 100% Natural, and it's a stunning color.
I adore makeup and could go on for an entire book on the subject, but I'll stop here and let someone else chime in!
Hopeless Romantic :)