Hi OP from what I'm making of your comments, I don't think you are after a whole new style, you just want a more stylish/polished version of the way you usually dress. This is absolutely ok, and easily achievable. It's also more sustainable than trying to change to a whole new look, because if you buy a whole lot of new current fashions, they will be out of fashion in no time and you'll be thinking you need to buy other new things and change your look again. Whereas you can look quite stylish and polished without looking cutting edge 'fashionable', and as a bonus can wear the clothes for many years to come.
If that sounds like what you are aiming for, my advice is that it is all about fabric quality and fit. So just look for the same categories of clothes you already wear (eg jeans, cardis, t shirts, all good) - but make sure they fit you properly and in a way you feel comfortable (eg hug the bits you like, skim the bits you are less keen to emphasise, have a flattering neckline and sleeve/waist length that suits you), and look for good quality fabrics, eg natural fibres usually look and last better than synthetics, thicker fabrics usually drape better than thinner ones.
Charity shops can be great, or otherwise as pp have said go to a few bigger stores for a big try on session to find the shapes and colours that suit you and you feel good in. Spend a bit more than usual and buy fewer items instead- but don't spend more on particular brand labels or current trends, focus on whether you feel good in them and whether they look of good quality. Buy only one or two things at a time and learn as you go, and most importantly, have fun with it! 