The French have an expression about a woman being comfortable in her skin ( bien dans sa peau ) which I think suggests she looks attractive, not frumpy.
This nails it. Of course it's the French who thought of it
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Being bien dans la peau involves identifying your best feature(s) and highlighting them. For instance, wearing grey head to toes to show off a nice tan and well groomed face and hair.
After you have done the basic decision making, it's all about balance as a pp suggested -- don't let your clothes and accessories shout each other out. Do either eyes or lips but not both. Scarf or necklace. Necklace or bracelet.
On the matter of practical vs good looking -- there isn't necessarily a chasm between the two. Don't try heels if you can't walk in them and if they are simply not practical. Nobody looks good hobbling along. When it comes to practical clothes like coats you will wear a lot, go for dark items, and buy good brands - North Face, etc. Imo dark always looks more chic than anything earth toned or bright, certainly for autumn and winter, and quality nearly always looks good.
Go for style over fashion. Where style is concerned, menswear is always a reliable source of inspiration. Tailored shirts and trouser style denim trousers can look better on women aged 40 and up than skinny jeans but again, if skinny jeans look good on you then take that with a pinch of salt. Any classic style whether preppy or punk or rocker -- can look good as long as you don't look as if you bought entire outfits straight from catalogue pages or mannequins. Don't wear 'costumes' in other words.
Hair style -- if your hair is straight and doesn't have a lot of body and your skin is pale, avoid blond highlights because they are going to wash you out unless you are prepared to pay a lot of attention to contouring your face and defining your eyes. Auburn shades or shades of red can be far more flattering for a pale complexion.
Above all, get a properly fitting bra, watch your posture, and wear some nice perfume that lifts your spirits.