History of the Franks by Gregory of Tours

This is a useful primary source, there are numerous translations in the ic. It is a history by a Christian Bishop covering Frankish history and gives good detail on the life of Clovis and his conversion to Catholicism and his impressions of it. It is bias, due to Gregory re-ordering the dates of some events to put Clovis in the light of a more pious convert, but nevertheless it is one of the most detailed portrtaits of a barbarian kings conversion available to us.

Res Gestae by Ammianus Marcellinus

Good account of a soldiers life (Ammianus) which contains details of the time he served under Julian in Gaul and Persia. It is pro-Julian in sentiment, but gives a good impression of why Julian was popular with soldiers for his effective command and handling of men. Goes on to detail his reign as Emporer and actions taken during this time. Number 871.9 in the information commons, only books 14-26 survive, so dont spend ages looking for the first ones.