Congratulations on getting to be able feel this!
How about starting with some fun, which will introduce you to different brands, and more importantly get your eye in:
www.collagerie.com
They do a weekly email.
I buy good quality clothes because if I choose carefully not only will they look good now, they will last me and can still be worn in many years time. My style is eclectic, and I don't really follow fashion very much. Brands I like which I think give good value looking at price vs quality, in no particular order are:
Max Mara
Joseph
Margaret Howell
Agnès B
Sandro
Paul Smith
Hugo Boss
Uniqlo
Cos
Arket
Individual boutiques can be a good place to start - there are very few left in central London, but ones that I like elsewhere are below - they sell some more unusual and interesting designers' clothes. Epitome in Edinburgh is a bit more edgy than I generally go for, but it sells high quality things, including fine Italian wool trousers, which almost never crease. I can't remember the name but a friend has some and it's amazing material and looks fabulous.
Cambridge
www.bownscambridge.com
Harrogate
www.morganclare.co.uk/designers/
Edinburgh
www.epitomeofedinburgh.com/#
dicks-edinburgh.co.uk/collections/womens-just-arrived
Newcastle (not a boutique, a department store)
Fenwicks
Mind, quality isn't everything, always. I went out with the same friend, she in her beautiful Prada silver slingbacks, me in my M&$ embellished velvet slingbacks that had cost £15 in a sale (but do look much much better than that, hence my recommendation that you 'get your eye in' so you know when something looks good quality). My friend's feet were sliding about in her all-leather Prada shoes so she couldn't walk that well, but my M&S cheapies, not having leather anywhere near them stuck to my feet so I could walk fine in them.