I completely understand the question, with every fashion magazine pushing its packed September issue on people as they check out at the grocery store, but really, who are these "trends" for anyway? Even someone who loves clothes as much as I do can't be bothered to worry about what Gigi or Cara are wearing, especially since they get most of their swag for free!
I think when it comes to dressing, quality is much more important than keeping up with whether animal print or leather culottes are the "it" item for a particular season. I look terrible in certain cuts of clothing and will never wear them. (Lookin' at you empire waist!)
Taking cues from what my current lifestyle demands ie. do I have access to a car or am I walking everywhere, is it hot in this city or do I need a coat etc. etc. I find it is much more satisfying to simply pay attention to cut, color, fabric and craftsmanship of any given piece, rather than try to assert any current cultural value to it. I look great in dark colors, jeans, well cut blazers, dresses (not separates), ankle boots and minimal jewelry, so that's what I own in multiples, even if this current city loves ruffles, seersucker, monogramming and pastels. (I'm in my beloved Charleston, SC.)
Determining what really suits you is a freeing process, and only then will you be able to truly cultivate a personal style. Plus you won't waste money on stuff you don't need, which will make you happier, richer and free up your closet for the things you love.
How do you know what suits you?
Mostly it has to do do with whether a particular item flatters your actual shape, not the shape you wish you had! For many years, in an attempt to ward off unwanted attention and to emulate various French fashion icons, I wore clothing that tried to hide my curves, which was largely unsuccessful! I eventually had to face the reality that I have BOOBS (shudder, SO not high fashion!) and pick more tailored options, lest I forever look pregnant and shapeless.
Whatever your body shape, you will have a great asset that needs to be highlighted! If you can't figure out what that is, ask a trusted friend, edit your closet accordingly, and then proceed to donate every item in your closet that doesn't make you look and feel amazing.
And stop buying magazines, they are only there to make you feel badly! (Small caveat, my friend Chris will appear in a major magazine next month, you should definitely buy that one!!)