I have been facing a similar problem as I try to build a more professional wardrobe which looks nice on me and is comfortable. Here is my advice based on my last year of shopping.
First pick a neutral: black, navy, tan, cream, grey
Pick the one you think looks best on you, and perhaps which matches somethings you already own (shoes, belts, tops...)
Once you have a base neutral you can reject items which will not look nice with that color so that your separates are easier to mix and match.
Buy a skirt, a top, a cardigan or two and/or blazer in that color. You may want to get two skirts, in different styles/lengths, or even a dress if you can find one. These items make a good base to build the rest of your wardrobe from.
Once you have these things, adding pieces is easier, as long as you limit yourself to things that match. If you buy a patterned skirt, you will know you have a solid top that will go, you will know you have a cardigan to go with a sleeveless dress, a solid skirt to go with a patterned top... and the solid pieces are easy to re wear without people noticing,
Styles of items:
Skirts.
I always picture you in full skirts, do you wear tighter ones too? If so I would say one full skirt and one a-line or even a pencil skirt. If you are comfortable with the silhouette, a high-waisted pencil skirt usually looks good on an hour glass figure.
Cardigan/blazer:
I recommend making the cardigan the best quality you can afford. I find mine are the best way to tie an outfit together, to cover something sleeveless, to turn summer clothes to winter clothes etc, so you want it to look great and wear well. Make sure it fits well, but is not too large. You want to be able to wear it buttoned or unbuttoned, but if it is too big it will look frumpy and not professional. The same goes if you opt for a blazer. Something simple that fits well.
Tops:
Tops are the hardest I think. I know that you like to dress more modestly than I do, and I know even I have trouble finding tops that cover me well. My standard top right now is a lace topped camisole like this:
it has adjustable straps, so there is some control over cleavage, and I wear them with cardigans, and sometimes under a dress that is low cut. These can be pricey (in my size anyways) but if you keep an eye out on clearance racks you can probably find something similar at a good price. I also grab for nice looking tank tops this time of year, again to wear under a cardigan. You can get these in any color or pattern that will go with your base neutral.
As far as button down tops, it's hard to find ones which wont gape at the breasts. My solution to this is to sew them shut. If you try on a top you like and it gapes when you move (but stays shut if you are still), you can blind stitch the placket and just put it on over your head. (Do you or someone you know sew, this is an easy job).
Dresses:
That dress you linked is lovely. I would say it is actually suitable, with a cardigan over it, to look pulled together and adult, but not too fancy. That is definitely a style that would flatter your figure.
Let me know what you think. And I would be happy to adjust based on your feedback (and to start prowling online shopping sites for you!)