By far the best-preserved and most useful Gothic text is the translation of most of the New Testament by Wulfila, contained in the Codex Argenteus manuscript in Uppsala. This manuscript, although incomplete in parts, gives us a good overview of Gothic morphology and grammar, and, to a certain extent, syntax (although it was translated from the Greek). Other materials, either Biblical or otherwise, may provide us with very different types of information; they may also, however, be of quite dubious quality.
The so-called Skeireins, a Gothic commentary on the Gospel of John, is perhaps the next most interesting source of information about Gothic. Written originally in Gothic, we assume, and most definitely not by Wulfila (most likely the work of two later clerics), it is often more indicative of “true” Gothic syntax than the Codex, since it contains many free passages, not based on Greek or Latin Biblical phrases. There are, of course, numerous quotes in the Skeireins from the book of John, but even these can be of some use to us, particularly where they alternate with the Wulfila manuscript that we have — these are mostly spelling differences, and may enlighten certain phonological questions and show the development of a later Gothic scribal tradition. In addition, the Skeireins, since it attempts to interpret the Biblical passages that may have been confusing to the Goths, is often a good source of cultural information: explaining the Roman practice of lying down for a meal, for instance, shows that the Goths most likely did not share this custom. Also noteworthy is the discussion of the “Arian heresy” in the Skeireins: the belief that God and Jesus were two separate entities (Jesus created by and thus subordinate to God), a dogma to which Wulfila and the Goths ascribed, but which was later declared heretical. Much of the Skeireins, however, is of questionable reliability: the manuscript was horribly damaged, written over with Latin script, partially erased, and finally “preserved” with nut gall, so that even deciphering the text itself is a monumental undertaking; in addition, the two scribes themselves were hardly masters of the art, omitting words and letters, correcting each other, and generally wreaking havoc with the text.
Two of the few non-Biblical samples of Gothic we have preserved are the title deeds of Naples and Arezzo. These deeds, notarized and signed by both Latin-Italians and Goths, show some native Gothic names, which are otherwise scarce (the Bible is of little help in this respect), as well as orthographical/phonological variation; however, the syntax of these deeds may be suspect, since they occur alongside Latin equivalents, and in such formulaic repetition as to negate their usefulness. Culturally, they are of some interest because they demonstrate the financial awareness and customs of the Goths, and also define more clearly the interaction between the Latin-Italians and the Goths, who for a time lived side by side.
Other sources of interest, both for linguistic and socio-historical studies, are the numerous citations in Latin texts of Gothic names, occasional phrases or sayings, or customs. Latin historians wrote commentaries and explanations of the “barbaric” Gothic culture, some of which are of course subject to bias, but which nonetheless tell us a great deal about everyday Gothic behavior, sometimes even transcribing drinking toasts or other common sayings. Other Latin texts include Gothic personal names, which can provide a great deal of phonological and orthographical information (e.g. the spelling of the tribe name itself: in 300 A.D. Latin scribes wrote Austrogothi, while by 400 A.D. it was Ostrogothi; some scholars point to this as evidence of the early diphthongization of Gothic au). These Latin texts are of little use in and of themselves, but in combination with other extant texts, they provide useful points of comparison.
Several minor fragments of Gothic text may also be worthy of consideration: the Gothic Calendar, a church Calendar from an Italian Gothic church covering only two months, is of limited value because it contains so little text, but it does provide some interesting forms (at least one of which, biláif, is the only cited singular preterite form of bileiban) and a great deal of information about the Gothic numerical and date traditions; in addition, it shows us what particular festivals and traditions this Gothic church followed. Runic inscriptions, dating from much earlier, are extremely problematic: not only are most of them badly damaged, broken, or eroded, but they are nearly all heavily disputed, since it is difficult to even determine their age or dialect, much less an actual meaning for the inscription. The Old Testament Book of Nehemiah is also extant in Gothic translation; it is most likely not by Wulfila (and I assume it is thus not considered “Codex” material), and can show some interesting variation in scribal and even syntactic structure, much like the Skeireins.
The final source of Gothic information is at once the most puzzling and the least useful. The Crimean Gothic attestations transcribed by the Flemish nobleman Busbecq are fascinating for their historical value: that a small enclave of Ostrogoths survived in the Crimea, nearly to the modern age, is truly amazing. Linguistically, however, relatively little is to be gained from Busbecq’s transcription. Firstly, he was no linguist, and his orthography is quite peculiar, showing corruption from his native Flemish as well as from German; so too, his primary informant was not a native Gothic speaker, but rather a Greek who claimed to be fluent in the language. In addition, we no longer have Busbecq’s original manuscript, but only a bad copy of a printed edition, full of errors and confusion. In short, scholars have managed to place this dialect into the Eastern Gothic family, showing as it does remnants of nominative -s endings, however dubiously attested. As such, Crimean Gothic does not tell us much about Wulfila’s Gothic, but it does provide an fascinating side-note to the history of the East Germanic dialects in general.