I'm especially interested in how (if this was the case) the political and socio-economic changed. Were the peoples of Ariovistus half nomadic tribes without much hierarchy? Did these evolve to stratified chiefdoms or other structures? (these last 2 questions are just to provide examples of what kind of answer I'm seeking)
The main social development among the Germanic peoples during 50 BCE-500 CE is the formation of increasingly larger confederacies; ie. the Franks, Goths, Alamani and Saxons, as opposed to the smaller and more autonomous tribes that came before them.
Germanic material culture and burial practices shows Germanic society to be highly stratified during the pre-Roman Iron Age. There are no known Indo-European agricultural societies that weren't highly stratified, so this is not at all unusual. Germanic peoples weren't nomads by the way, the idea that they were comes from the practice of some Germanic tribes to alternate between villages after depleting the soil; generally every 30 or 20 years or so.
The 1st century Germanic tribes wouldn't have differed that much from their 4th century equivalents. They had chosen kings and their society was divided between a nobility, various classes of freemen and slaves. All that really differed was scope and intensity.
To make a comparison with Ariovistus (most likely a Celtic name), he was in all likelihood hired by other Gallic tribes to fight the Aedui with the promise of settling on the left bank of the Rhine ... before he was defeated by Caesar and ended up in written history. Similarly the Roman Empire would make certain Germanic tribes foederati (allies) which allowed them to live within or next to the Roman Empire.
The difference was scale and continuity. The Roman Empire, compared to Celtic tribal politics, was - for a long time at least - a very powerful and stable entity. In forming political ties to the local Roman bureaucracy and providing warriors as auxiliaries to the Roman Empire in return of payment, the Germanic elite became stronger and their society (though never egalitarian) became more hierarchical.
To give an example, rather than a king being elected from all the nobles (as would have been the case during Ariovistus' time) in later periods they would have been chosen from but a few noble families (as among the Goths) or from a single large extended family, as seems to have been the case Franks near the end of the Roman collapse.
It should be noted though, that the true Germanic kingdoms only arose after the fall of Rome; and most if not all of them, emerged within former Roman territory; supported by an indigenous and (formerly) Roman upper class.