I am going to focus on clothing, as that's my area of expertise.

A lot depended on whether you were speaking of lowland or highland Scots. Lowland Scots were of the same Norman-intermarried with locals (call it Scots-Norman) heritage as their English cousins (and this would include William Wallace and Robert the Bruce and all of the Scots nobility.) Their clothing, armour, and equipment would differ little from English clothing of the same period. (The recent movie The Outlaw King generally got the look right, with some caveats--more for the women's dress than the men's.) Men and women wore cotes or tunics--men's full length, women's shorter--that in the 13th/early 14th century were generally loose and flowing with tighter sleeves and belted at the waist. Construction techniques generally involved straight seams and use of gores and gussets for fitting and to add volume through the body. (See Sarah Thursfield's Medieval Tailor's Assistant for diagrams of cut and construction).

It's regarding highland Scots where we just do not have a lot of evidence. Clothing historian Kass McGann has written a good overview of what we do know about Highland clothing here . To summarize, our best guess is that given the common Gaelic heritage and exchange between the Irish and the Scots in the early and central medieval periods, it is likely there were similarities in dress, including the use of the leine (which was usually made of linen, although McGann cites the Rogart Shirt of the 14th century, which was made of wool, as a possible guide to how it was constructed--which as you look at it, it's not too different than the cote/tunic widely worn elsewhere). The word leine means shirt, and per H..R McClintock's Old Highland Dress, as cited by McGann, only nobles would dye their leinte with saffron. I have dyed cloth with saffron, and this makes perfect sense--not only is it expensive, it is also used as a spice. (However, dying something with saffron means that you'll smell of crocus every time you get wet.) However, it is possible that those who could not afford saffron used other yellow dyes, such as weld, to get the favoured colour.

What would eventually become the great kilt (or belted plaid) of the 16th century was probably the brat, or the plaid (a word that means blanket), which was a thick, fuzzy woolen cloak. There is no evidence of anything resembling "clan tartans" at this early stage. There also may have been trews (pants) or additional outer garments, but there is just not a lot of evidence.

What strikes me about this period is that "Highland dress" during this period seems to have been more similar to iowland dress than different. It is really only when you go later, into the 16th century, that you see that the two styles have evolved in different directions