I feel you girl- particularly about clothing marketing to "rectangular shapes". Here's what I like to wear... tons of fitted tanks, blazers, cardigans and fitted sweaters. I'm personally big on solids, and dressing them up with cool accessories (printed scarves, cool necklaces, earrings...). I don't really wear a lot of the "flowy" tops that are in style right now because while they are cute, they just end up making my naturally hourglass figure look kinda boxy. It seems like it's all they sell though! I pair a lot of stuff with skinny jeans (black, denim, white for summer etc..), leggings (navy, black), and I skirts sometimes. Oh, and dresses (Love the sweater dresses!).
My advice: Find a muse. This could be celebrity that you think has a figure similar to yours, and also is a good dresser. One of my personal favorite fashionistas is the gorgeous Kim Kardashian. She has Killer curves and girlfriend knows how to work them. Then, see if you can copy her outfits (without spending all the money tough, lol).
1)don't shy away from belts- they're fantastic. The trick is the size of the belt. Wear it over something. Make it hit at the smallest part of your waist. Look up examples of good belt wearing.
2) One more thing- you're lucky. Hourglass figures are hot. so Rock it ;)