I'm mid 50's and have recently had my hair cut short from a mid-length bob. I have never had so many compliments on my hair ever! My boyfriend said it was the best haircut I've ever had and literally everyone who knows me, comments. I avoided doing it as I thought it would say 'old' but it's just the opposite.
Make up is really important. I've recently started using Clarins Beauty Flash Balm as well as a matte bronzer and have a subtle glow now which is a big improvement from the washed out look I was starting to get.
I still wear what I've worn for the last 7 or so years - skinny jeans, boots, t shirts, jumpers, parka. I've lost weight (gym and walking) and think they still look ok. I've been very aware of what not to buy that I used to buy on the basis it wouldn't be too becoming now - Anything with writing on it, pictures on it, anything frilly, flouncy, ethnic. I like well cut dark jeans, white t shirts, tan boots and chunky but simple jewellery. I've actually stopped wearing scarves (apart from winter outdoor ones) as they seem to highlight my slightly saggier jawline. With the new haircut, I don't feel I 'need' a scarf now.
Resist Per Una, animal prints, big earrings and statement jewellery is my advice and concentrate on hair, make-up, specs and clothes that suit your shape but that aren't fussy.