Iron follows the pattern of innovations appearing in the middle east, spreading later north and west to Europe. Iron production was pioneered by the Hittites in Asia Minor and spread through Greece and Italy from 1,000 BC on.
The Celts are linked with ‘Iron Age’ Europe, showing widespread cultural presence, especially from 800 BC to about 50 BC. I could not find good information on where the Celts came from nor where they went.
The following information is largely derived from the Landesmuseum Wuerttemberg in Stuttgart, Germany. At least initially, the Celts were centered in southern Germany, Switzerland and Austria. Later, they spread across Europe.
"The Celts are first mentioned in the writings of Greek historians around 500 BC. In archaeological terms they are usually associated with the Late Iron Age (450 – 15 BC) – the La Tene culture – but the roots of Celtic culture can already be found in the preceding Halstatt culture (800 – 450 BC). For this period we speak of ‘early Celts.’ From about 600 BC, we find in southwestern Germany, eastern France and Switzerland fortified central places whose social elites favored sumptuous burials under earth mounds. This type of burial characterized early Celtic Central Europe for a period of nearly 200 years.
The Wuerttemberg State Museum has been conducting research on local early Celtic centers of power since the early days of its foundation. Wurttemberg’s early state institution for cultural heritage also carried out excavations around the Heuneburg and the Hohenasperg." (sites in the region of Stuttgart)
"In the absence of written records, our understanding of early Celtic society is based solely on archaeological evidence. The degree of opulence of tombs and burial objects can be interpreted as indicating the economic and social position of the deceased. We find tombs built with enormous effort and expense and furnished with rich offerings as well as inhumations involving much simpler furnishings. Other dead were cremated, their ashesburned without any offerings. Such variations in burials and tomb furnishings suggest a highly structured society, with those found worthy of a ‘princely burial’ representing the elites. These social hierarchies are also evident in settlement patterns: hamlets, artisan settlements and farmsteads surrounding important central locations, the ’princely seats.’ "
"Ostentatious demonstration of power and prestige played an important role for early Celtic elites. Exhibiting high social status required a befitting manner and an outward appearance that corresponded to one’s rank. Clothing and jewelry were the main way of demonstrating elite status, both in life and in death. Their use was not limited to grave goods. As early Celtic garments are seldom extant, we depend primarily on precious accessories and on fragments of sumptuous head or neck jewelry to show that the early Celtic upper class also knew how to demonstrate their elite status in their lifetimes. Finds of various utensils for personal grooming emphasize this, such as exquisite imported pieces."