Everyone's idea of elegant is different, as can already be seen on this thread. That's why we need to know who you consider elegant OP. For me, it's Joanna Lumley who tbh can often look a bit frazzled, but she is always classy.
I also like Jennifer Aniston, I've seen her style criticised as "too safe" but again she always looks polished and classy.
I think as a PP said, always iron your clothes. When my kids were little I found that only ironing the front of most things worked fine.
Also it can be useful to have a limited colour palette so that everything goes with everything else. So my wardrobe has a lot of black navy and cream. Eg jeans, often the dark navy ones, a black blazer and an ivory
top. Then I add colour with accessories. It's safe, but looks good. And yes, cheap jewellery can look good.
Finally but most importantly, good grooming. So an easily maintained hairstyle, good skincare (doesn't have to be expensive just consistent), clean nails.
And finally, please stop wearing your DHs clothes, they're just not cut for women's bodies. Primark is fine, just avoid cheap looking prints. Good luck!