I am trying to get a grasp of all the ethnic groups and nationalities in Europe after the fall of the Roman empire from a broader​ perspective but I can only seem to find resources that focus on only one or a couple of these different people's at a time. The situation gets even more complicated because it seems like they were all moving around constantly. Where can I find a breakdown of all these different groups and subgroups without having to go through individually​ and piece all the groups without any context of everyone else at the time?
Some good reading on this subject can be found in Robert Bartlett's The Making of Europe and Thomas Charles-Edwards' After Rome.
At a very broad brush approach: The Gauls are the pre-Roman inhabitants of modern-day France. They became Romanised, and after the collapse of the Empire, remained predominantly in the "Occitan", the region of southern France bordering Italy and Spain.
The Franks were a Germanic tribe who acted as foederati for the Roman Empire, which essentially means they were allowed to settle in the border areas of northern Gaul, and in the wake of Roman collapse, expanded their power.
The Normans are a slightly different beast. The Vikings raided France extensively in the ninth century, and were eventually granted settlement lands in what is now the Normandy peninsula to essentially buy them off.