You'll have a great time, few things better than deer stalking in Scotland!

Generally speaking the attire requirements/expectations for stalking vs. shooting are quite different. For shooting you tend to have all traditional requirements: breeks, tie etc.

I've been stalking on 3-4 estates in Perthshire and what I've seen is less traditional. Generally similar to what you'd find in other cold weather hunting places: Northern, Europe, Canada, USA, New Zealand. Mixture of US camo hunting/Cabela's stuff, water proof micro fiber, fleece, etc. About half the people I've seen over the years wear tweed breeks or plus fours. Truth be told since I love the history of deer stalking in Scotland I'm perhaps the most "traditional" guy I've seen out stalking. I normally wear leather lace up boots, waterproof long socks, tweed plus fours, button up fleece shirt, surplus commando pull/sweater, and waterproof Jack Pyke jacket (normally too warm for the jacket), and either a tweed flat cap or a deer stalker hat. I'll add my dad and I are the only people I've seen wearing deer stalkers on the hill.

The kit is practical and its traditional enough for my tastes. I don't like camo if I don't have to wear. A bit part of hunting for me is the tradition and "getting away" from modern life. So having a bunch of super high-tech clothing like I stepped out of a Discovery Channel fake survival show is not my cup of tea.

I'll put in a plug for a good set of plus fours in tweed. As mentioned earlier you'll get a great set of leg mobility from plus fours and the tweed will stand up to all sorts of brambles and heather. The vintage stuff is better than most of the modern stuff, it was made to be used. Lots of the modern tweed stuff I see in the shops seems more for "Sloan Ranger" types in the city. You can find good and cheap vintage breeks and plus fours on British ebay with a little looking.

Here I am with the keeper for this estate, I've got tweed plus fours he's in tweed breeks: