Before 70 AD Scotland was made up of groups of Celtic people clustered round hill-forts. (see Atlas of Hillforts in Britain and Ireland.) The people of Scotland spoke Brythonic, a Gaelic language similar to Welsh, Cornish and Breton. We know this from place names such as “Aber” which means confluence, “Strath” which means wide valley and “caer” which means fort. They lived in roundhouses and their diet was predominately meat eaten as a stew. They lived in a land of cairns and stone circles built after 3000 BC. They used chariots as shown by this Newbridge Chariot Reconstruction, made swords and worked iron.
They wore little body armour. They traded across Britain with flints from York found in the north of Scotland and internationally with links to southern France as shown by the Stirling treasure trove. See Iron age gold torcs. Women wore clothes made of wool, lamb skins and plant fibres. The clothes were dyed various colours. See The Huldremose woman’s clothes for an example found in a bog in Denmark.
The tribes of Scotland were documented by the map-maker Ptolemy in Alexandra, Egypt 150 AD with the Caledonii being the best known today.
Here is a link to an academic paper detailing Iron Age Scotland :SCARF Panel Report.
The Hunterian in Glasgow has a web page on Iron Age Scotland.