Depends on person, preference, terrain and 'requirement'.
In reverse order - some circumstances/ estates have an expectation. Ultimately as the client you have final say. There maybe a requirement to be shirted & tied etc - if in doubt ask.
Terrain - the Scottish 'Hill' covers a multitude. as has been noted it can be actually quite flat through to giving a Billy Goat vertigo vertical. If in doubt ask. Wellies tend to be a poor choice for anything involving extensive walking. Ankle support is worth its weight in boot leather. But the absolute over-rider is comfort. Boots that cut or blister can make a pleasure purgatory. Occasionally valued comfy boots show a mean streak if you have to move fast, walk a side slope etc. Stopping at John Norris on the way up to get a pair is living life 'on the edge'
Some hills are quite dry, some not. Caithness will soak you through even in head to foot PVC. Expect to get wet and make every effort to avoid, but be aware its a chance.
Including weather in terrain, a full day on the hill can see blazing sunshine, driven rain, sleet or snow, fog etc etc. No one outfit will perfectly cover that - but some come close with the deft use of openings - zipped or otherwise.
If in doubt worth asking as to likely method used when out. Dressed to cope with a stiff climb, you will get severely chilled on a long Argo ride or laying waiting out an animal.
Preference - looking the part makes you feel the part. Its your day ultimately. Nothing out weighs being comfortable.
Person - an ultra thin racing snake is more likely to be concerned about staying warm and a chunker more with staying cool. I love the look of smock type jackets, but know that I'd combust in one on the hill. The official definition of winter in moray is when I zip the under arm vents up on my Ram jacket..
Its an old saw, but layers are wonderful. Never be reluctant to stop and adjust clothes - adding or subtracting as you need and thinking ahead - stop and take that jumper off before charging up a hill etc. As soon as you stop - put it on - dont wait for you to notice too hot/cold.
Material - tweed is popular for many reasons. Its a personal thing, but I think tweed +2/+4 are great. Not keen on itchy/scratchy heavy stuff - really like the Barbour stuff. Ticks are an issue not to be ignored, but not having trouser leg below the knee makes for easier walking over the length of a day.
Modern is good - at times, but nothing breathable turns out to be that breatheable or waterproof. I'd rather rely on good ventilation - under arm zips etc that wonder technolgy - I must be alone in that otherwise some great jackets out there would be fantastic jackets!
I like tweed plus 2/4, with light top shirt, jumper if needed, waistcoat if needed and Ram jacket or similar. If its going to throw it down I find slicks hard to beat - but slow right down so dont get soaked inside.
Gaiters - sorely miss the Kammo ones. Never really gone for just high socks - collects every heather seed on the hill.
Hope that helps. Just be aware that developing the full 'power band' look takes years of dedication....
