I really, really need some advice on finding a look that suits me, that is practical, stylish and age appropriate. I'm heading towards 40 and have so little confidence in my appearance, I know I'll never be one of those effortlessly stylish people but I'd love to feel more comfortable with myself - just haven't a clue where to start 
I'm 5'3 and a size 14ish (down from a generous 18 this time last year thanks to WW) with fairly big boobs. I haven't got a fortune to spend on clothes but would prefer to buy a couple of goodish quality bits and build up a wardrobe that evolves rather than constantly buying new things that don't go together or even suit me.
At the moment I mainly shop in Gap (plain t-shirts), New Look (jeans), M&S (leggings, cardigans and t-shirts), White Stuff (plain tunics, not fond of all the heavily patterned stuff) sometimes Next (but much less so lately) or surfy type places like Animal.
I work from home so don't need anything that smart, at the moment I live in jeans or leggings with plain t-shirts or tunic tops and boots or Converse. I have tried livening my look up with accessories (have a multitude of scarves and necklaces) but nothing looks right and I read a lot of magazines to get ideas but most of the clothes either look ridiculous, are way out of my price range or are much too formal/impractical for my lifestyle.
I've also been following this blog wearingittoday.blogspot.com/ and I really her style, a lot of the stuff she wears is very much to my taste (stripes, plain simple shapes, not too much pattern) but somehow I don't carry it off in the same way - of course it helps that she is very slim and pretty
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I feel that if I play it safe I look a bit boring and mumsy but if I am more adventurous I often end up feeling tarty and inappropriate.
What is a 'suitable' look for a mum who's not that young any more but doesn't want to go down the Boden uniform route? How do I find a style that's my own, that suits my lifestyle and my age, that I am comfortable with and that doesn't fall into either the mumsy or mutton categories? Where could I try shopping and what sort of things should I be looking for? Are there any definite no-nos?
Very grateful for any ideas or advice :)