Sorry I’m late to this but here are my tips!
I’m in the Lakes so learned pretty quickly how to do it - and it is almost backwards thinking to how we usually dress for more urban pursuits, etc.
Avoid cotton like the plague.
Depending on budget - and you can go in at cheaper end mountain warehouse all the way up to Rab/Patagonia, etc for brands.
I’d recommend a merino baselayer for winter and a sweat wicking base tee or top for summer.
Ideally a mid layer - thin fleece or breathable zip up/hoodie.
On top, for winter, a lightweight synthetic food away puffer. This can be taken on and off during walk and weighs no more than a sock!
This is a superb blog post with recommendations. She is a hill walker but explains the technicals very well, including accessories.
You can get all of these at low prices and do not need to commit to the pricier brands.
Most of the advice on MN regarding quality clothing works oddly in reverse here, so wool and cotton would trap sweat, synthetics are your friend in this dept.
Here’s the link - wildandwords.com/blogpost/what-i-wear-for-hillwalking