OP, if you feel shy about bra fittings, I use the Reddit abrathatfits calculator and find it extremely accurate:
https://www.abrathatfits.org/
Much better than the in person fittings I previously got at M&S and Victoria’s Secret. I just order online; sometimes takes a couple of goes but I always end up happy with the fit. I too have lost a lot of weight and so I have to be careful with the shape of the cup; lots of bras will distort the shape if you’ve got lots of loose skin (which I do!) so need full cup or balcony.
I like the shape of your polka dot dress. I’m also playing around with style after massive weight loss and have to say I’ve started to be a bit pickier with fabric as lots of viscose and blends will cling in a way I don’t like. The same shape in cotton may flatter you even more. It’s all trial and error though.
I’ve bought a lot of stuff very cheaply on Vinted as to really work out if something suits you you often have to wear it properly rather than just try it on. I’ve slowly become more confident experimenting more widely with shapes and styles; I think wearing more variety can really help get your eye in. I agree with pps that the concept of “style”
as a set of restrictive rules is utterly boring. I live in London and there are so, so many ways to dress that look good.
90% of those online styling videos seem to just be taking a normal outfit and adding shoes, a handbag and maybe a scarf or necklace! I never really got the deal with accessories but bought my first handbag recently at the ripe old age of 41 and have to say it has improved my stylishness. So maybe look into buying a bag you really like, sunglasses, sandals you don’t hate, jewellery? Accessories can seem less urgent if you’re trying to build a wardrobe of actual clothes but I’m suspecting they punch above their weight.