Assuming you're concentrating on the late 1600's-early 1700's, as previously mentioned:
-you need more than just a shirt of linen or cotton. Add a wool overshirt, or a wool waistcoat or short jacket
-don't forget some sort of canteen or leather water bottle
-here's a lightweight, period-type fry pan with folding handle
-haversack, used by civilians as well as military
-the stocking-worn sgian dubh doesn't appear until the 19th century. Your highlander would carry a small sgian, for skinning game and such, in an armpit sheath, as a side knife on his dirk scabbard, or in his jacket pocket or sporran.

-unless you're used to long hours in 'em, I'd go with hard-soled shoes instead of cuarans ("moccasins")
-the wider, knitted, period bonnets can't be beat. Worn tugged straight forward (not cocked to the side in the modern manner), they will keep the sun and rain out of your face

-your basket-hilt sword can be carried quite comfortably if you hike it up onto your lower back by cinching up your baldric (sword belt) to one of the higher belt holes.
-I'd be carrying my sweet, lightweight (6.5 lbs) flintlock fowling-piece, but that's just me...