Why on earth does age matter, if you want to know what looks stylish?
There is so much more to choosing clothes, and how they look on you, than the date of your birth certificate.
I am not in your age range, so stop reading now if you want. But I find dresses are the solution. What is the issue with your current ones?
Look for natural fibres (extending to loose viscose, as it's plant based) and looser fits. I had a lovely 'school run' dress (MN jargon sense, nothing to do with actual journeys) from TKMaxx, whuch was sleeveless shirt style (so loose fit, but can be belted so you aren't shapeless. Lots of stripy, longer more flowing dresses around, in lighter fabrics, and they shouid be cool.
I wear shorts a lot as well, with either Converse/trainers or espadrilles. Looser tops that drape well when it's hot. Nothing tight (though you need narrow shorts, to avoid looking 1980s - unless that's the look you want?
If chafing is an issue, try Body Glide rather than adding more clothes