It’s taken me a while to RTFT which is why I’m a bit late to this but hope this will help OP and anyone else struggling with how they present themselves to the world:
There have been a lot of personal tales of “how she does it” along with a lot of “rules” - wear white shirt/jeans/blazer! Ugh, wear anything BUT white shirt/jeans/blazer! etc.
Well, it just so happens that white shirt/jeans/blazer works really well on me when I accessorise it with red patent stiletto courts and a silk scarf, so “rules” are generally quite useless when dealing with the visual image of someone you’ve never seen!
Still, the main points to take away from all these tips that I see are the following:
— what these ladies - and men - have done is find what works for them. It has invariably involved some trial and error, and mistakes, but they’ve clearly used those mistakes as learning opportunities.
—the fit of your clothes really is paramount. You cannot feel together and polished if you are constantly tugging your jumper past your bottom or pushing your sleeves up. If you can’t buy them fitting properly then it is worth it getting them tailored to fit. (They say this is one of Holly Willoughby’s secrets - she is the queen of high street clothing but has a seamstress on speed dial to tailor anything that doesn’t fit perfectly.)
— it will help you tremendously in making sure your clothes fit if your body is in a shape you are comfortable with, and therefore it is worth it to do whatever you need to do to get into that shape.
— a skincare and “maintenance” regime in areas like hair, nails, makeup etc. that works with the time and money you have - but again, achieved through much trial and error - will pay off in terms of savings when time and money are temporarily short.
— the most important point to bear in mind is that running through every single post from a person who takes care of their personal appearance is a conviction that they are worth it. They deserve to feel that they look well and that they have self-respect and pride. It isn’t frivolous, it isn’t selfish, it isn’t trivial. You don’t need to apologise for it or feel ashamed of it. You don’t owe anyone a justification or explanation.
It is this last point that I will admit has been hard for me. My DH has slightly let himself go a bit - he works from home with just the dog for company most days and can go weeks without shaving. He loves being outdoors and fits in a lot of house maintenance (which, don’t get me wrong, is rather valuable!). Though he can clean himself up rather well when he wants to (how else would he have attracted me?), he does sometimes give an impression he thinks his lack of interest in his day to day appearance is a virtue. I have recently returned to working in the City after 4 years at home with him. While I have always been smart when going to work, at home I started taking his attitude on and didn’t see the point in dolling myself up just for the school run or to dash to the supermarket of a weekend (well, I might if it was Waitrose 
).
Well, I’ve changed. One Saturday morning while he was out with DD I showered and coloured my hair and exfoliated my face. Weight Watchers had just kicked in and I could see it in my face and clothes. I put makeup on and dried my hair and really liked how I looked. I went shopping for DCs’ birthdays and every time I caught my reflection in the mirror I was actually pleased!
I deserve to feel like that as much as possible, even if I’m just hanging round the house. While I wouldn’t say I’m fanatic now about grooming, I am diligent and use my Saturday mornings for general maintenance. And it hasn’t changed my relationship with DH in the slightest! If anything, he is complimenting me more on how nice I look. I do it for me but it is nice he notices.
I really hope OP and everyone else who wants to improve their appearance takes this on board: you owe it to yourself to put the best you forward you can. You can do it!