The plus size woman often doesn't have a lot to choose from when it comes to basic garments - I'm thinking of what is IN her wardrobe now, rather than what is on offer in the stores.
Many thousands of women today are limited in their budgets - whatever many young people may think. Older women in their 30s onwards have to strictly constrain their spending, and this is where buying good quality garments when they are available, in colours and fabrics that will be complimentary whatever the season, can form the basis of good style.
So if you have some good pants, skirts and jeans, then it's only a matter then of choosing some tops and jackets that will mix 'n match with each other as well as the basic pants, jeans and skirts, and you can find yourself with combinations that will always make you look good, and when you look good, you'll feel good.
As an aside, one of my friends in the USA does her own dressmaking. She has proven patterns for her pants and she usually wears black. But her tops and shirts are a riot of colour. She changes the hemline, the neckline whether v-line, low round or with a collar, she changes the length of sleeves, and her tops and jackets are always commented on favourably by those who know her and see her. She always looks smart, and you forget that she is plus-size, because she's learned to use colour that suits her complexion and her personality.
I love "layering". To use different tones of one colour and have a contrast makes so much sense. And again mixing 'n matching can achieve wonders. Scarves of every width, and length and pashminas can turn a garment into layers without even trying.