I'm older than you but I am often mistaken for being younger.
So, not sure if I can help but...
I think floral or flowery dresses tend to be unflattering on older women unless they are very stylish and 'occasion' dresses.
They are just 'boring'.
I see my Mum's friends in their 80s wearing Seasalt/ White Stuff type of dresses.
The quality is awful with WS, and SS just says 'old' to me.
I think that weight is a factor. We can't see you and a 14 may be slim and curvy, but no waist is ageing. If you need to lose half a stone, do it.
Unless you're carrying rolls of fat on the tummy, wearing dresses that are more fitted often looks better than tent-like shapes. Tent-like just says 'I'm fat and trying to hide it'.
I tend to look at brands that are perhaps meant for younger women but I am careful what I choose. Nothing sleeveless - upper arms are flabby. Nothing with lots of girly frills.
I buy from Nobody's Child (they have a lovely light denim midi dresses).
I like Hush but they are too long.
I buy Boden but almost always plain colours not garish prints. They tend to be shirt-waist midi styles (mid calf for me) with a fitted belted waist and a full-ish skirt.
I've also had some nice stuff from J Lewis and their own brands of Anyday and And/Or.
I used to buy Jigsaw but they are £££. Their outlet or sales are good.
For knitwear I sometimes splash out on The White Company and buy one nice jumper (wait for the sales.)
I've not bought from M&S in years but their dresses seem to have improved this season.
I've recently stopped wearing skinny jeans all the time and got some looser boyfriend style (not crazily baggy) which I've had compliments on from my very stylish daughter in law.
Why not look at the fashion pages in magazines meant for women our age?
Good Housekeeping, Platinum and Woman & Home?
Not saying follow it slavishly but you might get some ideas.