I find that a combination of nice slacks and jacket with a sleeveless shell underneath works well for most work-related occasions - or longer skirts with a nice blouse. I generally find jeans uncomfortable and heavy, though I do wear them. I have also been known to wear my nice riding boots (low heels) in the winter with the slacks. In the summer I do like nice skirts and blouses - but I never wear heels - ever. (Too many foot problems for that and I never did learn.)

The important thing, as others have noted, is that you need to be comfortable in what you are wearing. The nicest of outfits just won't look right if you don't enjoy wearing it.

As far as the blazer/jacket question goes - to me the difference seems to be the weight/type of the material and the style. I don't care for blazers myself, they don't seem to go well with my shape. Call them what you will though, if it looks nice with what I have in mind and on my body I will get it