I think I "get" what you're looking for OP?
that stylish BUT comfortable and "outdoorsy" thing where you aren't too "dressed up" vs "not dressed up"? I think what's commonly called the "posh" look actually is just "practical can do anything in this outfit".
This is my outfit for a day in London which took me from looking round a college, then seeing some museum, then being treated to a vair expensive dinner might have also bought myself a cheeky solo Mcdonalds breakfast in thereblush
Trenchcoat (charity shop)
Comfy boots - THESE in brown. Long boots are leg-flattering and practical
Pink TM Lewin shirt (charity shop - closest I can find online is this) without frills.
Short green skirt (grown up version of THIS
I'm no make-up, but I have spent AGES picking my glasses, getting the "right" haircut so I think my face is flattered. I actually have thin hair so a shorter cut with layers works for me. don't do nail varnish or fake tan
jewellery - plain silvery heart necklace, one silver watch from charity shop.
In general I go for:
well-cut coats, scarves, berets
knee length boots galore
ballet flats in light colours, not too shiny except metallic
faux pearls, not for a particular "look" but i think white sets off other colours very well?
also practical is good - I have a barbour and long dramatic coats not to look more "country" or more "opera grand damme" (although I go to both - my family didn't but I enjoy them) but as they're brilliant for walking about the city in bad weather.
dresses dresses dresses! charity shops have some brilliant ones. plain dress (in strong colour) well-cut (so not too much skin but more shape) ballet flats, sunglasses.
well cut jeans, chinos, worn with plain black top and a tiny scarf.
Agree teeth, fitness, posture, hair, probably important thing to concentrate on.
also what colours, shapes, works for your figure might be a matter of trial and error. also if you want to explore more arts and culture depends on where you live but JUST DO IT. you can go to opera alone, and art galleries are MADE to be walked round alone. youtube has loads of free opera.