It is not what you wear, it is the way that your wear it.
If you feel frumpy and old, you will look it no matter how you are dressed, have your haircut etc etc. We all know people who are ageless not because of what they wear but who they are and expensively dressed lumps, who are that because their minds are lumpy and down.
So start be loving yourself, book yourself a pampering day somewhere, at a spa or wherever. While you are there leaf through all the magazines looking at hair styles, fashion styles etc, forget that the fashion ads are posed on stick thin models in bizarre positions in ridiculous combinations of clothes. Just look at the clothes and what you are looking at that you like and would suit you and next time you are clothes shopping, whether at a supermarket or Bond Street look for those shapes and colours.
As for heels - they are so yesterday, everyone wears flat shoes these days. I am the same height as you and I am currently wearing black patent leather loafers. My shoe wardrobe includes flat ankle boots, more loafers in other colours and boots with 2in very chunky heels.
The world is your oyster, you can soon look really good for your age, it is all in your mind.