Some new info on the Goths from a book I am reading, Empires and Barbarians, by Peter Heather.

The Gothic migration south from the Baltic to the Black sea was much larger than previously thought. There was at least 6 different Gothic political units each with their own leader. By the time the Huns arrived on the scene, the Goths were spread all the way up and down the eastern side of the Carpathian mountains. And 1000 kilometers to the east along the north coast of the Black sea to the Crimea. In addition, 2 new Vandali groups show up, the Astingi and the Lacringi. They had joined the Goths. Here is how the Roman historian Procipius described the Vandali: They resemble the Goths in language and in all other respects. In addition, other Germanic tribes showed up in this migration south. The Heruli, the Gepids, the Taifali and the Rugi. They all probably spoke the Gothic language. The total numbers may have approached a half a million. When the numbers get this big the people are called a nation.
These were "peoples", a closed biologically self reproducing group whose members shared pretty much equally in a distinct cultural identity.
This changed once the Huns arrived on the scene. It was more a question of forming alliances just to survive.